By the end of this lesson you will be able to
- Open System Monitor or Task Manager and read the CPU, memory and disk graphs.
- Tell a normal busy moment from a sustained problem.
- Disable a startup application you do not need and say what the change does and does not do.
- List the warning signs that mean you should stop and seek professional repair.
- Prepare before taking a computer for repair: back up, note symptoms and avoid scams.
In the last module you ended a frozen program. This lesson goes one step further: learning to read the graphs that show what your computer is doing, and to decide what runs at start-up. Those two skills explain most slow starts. We also say clearly when to stop trying to fix things yourself, because the wise answer to a failing drive or a swollen battery is a professional, not another experiment.
What the graphs show
System Monitor (Ubuntu) and Task Manager (Windows) draw live graphs of three resources. The CPU graph shows how busy the processor is, as a percentage. The memory graph shows how much of the RAM is used. The disk graph shows how much reading and writing the storage is doing. Each graph answers one question: is this resource the bottleneck? A bottleneck is the part that everything else is waiting for.
CPU: 12% Speed 2.6 GHz Processes 214
Memory in use: 9.4 GB of 16 GB
Short spikes are normal.
A flat line near 100% for minutes is a problem.
- Marker 1: Click an entry to see its graph
- Marker 2: How busy the processor is now
- Marker 3: Memory use under about 80% is comfortable
- Marker 4: Sustained 100% means a bottleneck
Read this figure as text
A simulated Task Manager window with a sidebar of CPU, Memory and Disk and a main area showing percentages.
A simulated Task Manager window on the Performance page. The sidebar lists CPU 12 per cent, Memory 61 per cent, Disk 0 per cent and Wi-Fi (mark 1: each entry is a graph you can click). The main area shows the CPU graph with a percentage of 12, a speed of 2.6 GHz and 214 processes (mark 2: how busy the processor is right now). Below it, memory in use is 9.4 GB of 16 GB (mark 3: memory use below about 80 per cent is comfortable). A line says that a short spike is normal and a flat line near 100 per cent for minutes is a sign of a problem (mark 4).
Open the monitor and find the graphs
Ubuntu: System Monitor
Step 1: Open it
Press the Super key, type
System Monitorand press Enter. If it is missing, install it from App Center.You should see: A window with tabs: Processes, Resources and File Systems.
Step 2: Open Resources
Click the Resources tab. It draws history graphs for CPU, Memory and Swap, and Network.
You should see: Coloured lines move from right to left over about a minute.
Step 3: Check File Systems
Click File Systems to see how full each disk is.
You should see: Each disk shows total, free and used space and a bar.
Windows 11: Task Manager
Step 1: Open it
Press Ctrl, Shift and Esc together.
You should see: Task Manager opens on the Processes page.
Step 2: Open Performance
Click Performance in the left menu (the speedometer icon). Click CPU, Memory and Disk in turn.
You should see: Each page shows a live graph and numbers.
Step 3: Read the processes
Go back to Processes and click the CPU, Memory or Disk heading to sort by the busiest.
You should see: The program using the most of that resource moves to the top.
Reading the graphs calmly
A graph moving is not a fault. The processor is meant to be busy when you open a program or start a video, then fall back. What matters is the pattern over minutes. Use this table to tell normal from worrying.
| Resource | Normal | Worth investigating |
|---|---|---|
| CPU | Spikes when you open programs, then falls to a low value | Stays near 100% for minutes with nothing running; the fan is loud |
| Memory | Rises as you open programs and falls when you close them | Near 100% all the time, or one program's memory keeps climbing while you do nothing (a memory leak) |
| Disk | Brief bursts while saving or starting programs | Active time near 100% for long periods, especially on an older spinning disk |
| Network | Bursts when browsing or downloading | Constant heavy use when you are not using the internet |
- Spikes when starting things
- Falls back afterwards
- Memory falls when programs close
- Short bursts of disk activity
The computer is doing its job.
- Flat near 100% for minutes
- Memory climbs while idle
- Disk busy for long periods
- Loud fan, hot case
Find the program, close or update it, check heat and storage.
Read this figure as text
Two columns comparing a normal graph that spikes and falls with a worrying graph that stays high for minutes.
Two columns. Column 1, Normal: the graph spikes when you open a program or start a video, then falls back to a low level; memory rises as programs open and falls when they close; short bursts of disk activity. Verdict: the computer is doing its job. Column 2, Worth investigating: the graph stays near 100 per cent for minutes with nothing running; memory keeps climbing for one program even when you are idle; disk stays busy for long periods; the fan is loud and the laptop hot. Verdict: find the program using the resource, update or close it, and check for heat, storage and malware.
When a graph is high, go to the Processes list, sort by that resource and read the top names. Many are ordinary: a browser with many tabs, a video call, a program indexing files after an update. A program that is high and idle is the one to update, restart or reinstall. Do not end processes whose names you do not recognise.
Startup applications
A startup application is a program that starts by itself every time you sign in. Some are useful (your security software, a cloud storage tool, a printer helper). Others are left behind by programs you installed once. Each one uses memory and a little processor, and together they lengthen the time before the computer is ready. Turning one off does not uninstall it. It just stops it starting automatically. You can start it by hand whenever you like, and you can turn it back on.
- Marker 1: High impact: disable if not needed at once
- Marker 2: Keep tools you rely on
- Marker 3: Never disable your security software
- Marker 4: You can re-enable it later
Read this figure as text
A simulated Task Manager Startup apps page listing programs with Enabled or Disabled status and a startup impact of High, Medium or Low.
A simulated Task Manager Startup apps page. A list shows four fictional programs. Example Chat: Enabled, High impact (mark 1: a candidate to disable if you do not need it at once). Cloud Sync Tool: Enabled, Medium impact (mark 2: keep it if you rely on it). Printer Helper: Disabled, Low impact. Security Software: Enabled, Low impact (mark 3: leave your security software enabled). A right-click menu offers Disable (mark 4: you can turn it back on with Enable).
Control what starts with the computer
Ubuntu 24.04
Step 1: Open Startup Applications
Press the Super key, type
Startupand open Startup Applications. If it is not installed, it can be found in App Center under that name.You should see: A list of programs that start when you sign in, each with a name and a comment.
Step 2: Untick the program
Untick or remove only a program you recognise and do not need at start-up, such as a chat app. Leave unfamiliar entries alone.
You should see: Next time you sign in, that program does not start by itself.
Step 3: Test
Restart and check that the computer is ready sooner. Start the program by hand to confirm it still works.
You should see: The program opens normally when you choose it.
Windows 11
Step 1: Open Startup apps
Open Task Manager (Ctrl+Shift+Esc) and click Startup apps, or go to Settings, Apps, Startup.
You should see: A list with a Status column and a Startup impact column (High, Medium, Low or Not measured).
Step 2: Disable one
Right-click a program you recognise and do not need at start-up and choose Disable. Do this for one program at a time.
You should see: Its status changes to Disabled.
Step 3: Test
Restart and see whether the computer is ready sooner. If anything you needed has stopped working, return and choose Enable.
You should see: The program still starts when you open it yourself.
When to stop and seek repair
Everything so far assumes the fault is in software. Some faults are in the hardware, and no setting will cure them. Trying to fix these yourself can make them worse or put you at risk. The table lists clear warning signs.
| Sign | Why it matters | What to do now |
|---|---|---|
| Clicking, grinding or scraping from a spinning hard drive | The drive is failing mechanically | Back up at once if it still works, then switch off and get it checked |
| Disk or SMART warnings; 'No bootable device' or 'Operating system not found' | Drive failing or system damaged | Stop heavy use, back up if you can, ask for repair |
| Swollen battery, case bulging or lifting, burning smell | A swollen battery can burn or leak | Switch off, unplug, stop using it, take it to a repair shop |
| Liquid spilled on the keyboard | Corrosion can start within hours | Switch off at once, unplug, do not switch on; take it for repair |
| Cracked screen, bent hinge, loose ports | Physical damage that gets worse | Stop using and book a repair |
| Overheating and shutting itself down, even after cleaning outside | Fan or cooling failure | Ask a repair shop to clean and check the cooling |
| Many different programs crash and a clean restart does not help | Possible memory, drive or other hardware fault | Back up and ask for help |
- Burning smell, swollen battery, spilt liquid or visible damage?
- YesDo thisSwitch off and unplug. Do not switch on again. Take it for repair.
- NoClicking or grinding noises, disk warnings, or 'operating system not found'?
- YesDo thisBack up now if you can, stop heavy use and seek repair.
- NoDid it start after an update or a new program?
- YesDo thisTry the safe steps: restart, updates, startup apps, remove the new program.
- NoDo thisFollow the troubleshooting method. Ask for help if it does not improve.
Read this figure as text
A yes or no decision tree that separates dangerous hardware signs from software problems you can try to fix yourself.
Start: something is wrong with the computer. Question 1: is there a burning smell, a swollen battery, spilt liquid or visible damage? If yes, switch off, unplug and seek repair, and do not switch on again. If no, question 2: does the computer make clicking or grinding noises, or show disk warnings or a missing operating system? If yes, back up at once if you can, stop heavy use and seek repair. If no, question 3: did the problem start after a software change such as an update or a new program? If yes, try the safe software steps in this module, such as restart, update, startup apps and removing the new program. If no, try the troubleshooting method, and ask for help if it does not improve.
Before you hand it over
- Back up anything you can, if the computer still starts. Do not run a drive that is making noises for longer than needed.
- Write down the symptoms: what happens, when it started, what you tried and the exact error messages.
- Guard your passwords. Share a sign-in password only if the repair truly needs it, ask the shop what they need, and change important passwords afterwards if you did share any.
- Choose a trusted shop. Ask friends, check reviews and ask for a written quote before work starts. Ask whether data will be kept private.
- Compare repair with replacement. A repair costing more than half the price of a similar new laptop may not be worth it, especially if the computer is more than five or six years old.
Common mistakes
✖ Instead of: Disabling every startup program at once.
✔ Do this: Disable one at a time and test. Keep security software and anything you cannot name.
✖ Instead of: Panicking at a short CPU spike.
✔ Do this: Watch the pattern over minutes. Spikes while you work are normal.
✖ Instead of: Using a computer with a clicking drive 'one last time' without backing up.
✔ Do this: Back up carefully if it still works, then stop and ask for repair.
✖ Instead of: Giving remote access to a stranger who called about a 'virus'.
✔ Do this: Hang up. Genuine support does not cold-call you.
If something goes wrong
- Startup Applications does not appear on Ubuntu.
- Search for 'Startup' after pressing the Super key. If nothing appears, look in App Center for 'Startup Applications' or ask for help.
- The Startup apps list is empty in Task Manager.
- Make sure you opened the Startup apps page (not Processes). You can also use Settings, Apps, Startup.
- The computer is still slow after disabling startup programs.
- Look at memory, disk and heat in the monitor. A nearly full drive or an ageing spinning drive may be the cause; see the earlier lessons and consider repair.
- I disabled something and a feature stopped working.
- Go back to the same list and choose Enable (or tick it again), then restart.
Key terms
- Startup application
- A program that starts by itself every time you sign in to the computer.
- Memory leak
- A fault in which a program keeps using more memory over time and does not give it back.
Practise it for real
Reading is not the same as being able to do it. Complete these on your own computer, then tick only what you have actually done. These ticks are your own honest record: nothing checks them for you.
Watch the graphs while you work
Open System Monitor or Task Manager and keep the CPU, memory and disk graphs on screen. Open your browser, then a video, then a large document. After each, note how the graphs change and how long they take to fall again. Close the programs and note what happens. Look at the Startup apps list and count how many are enabled. Disable nothing yet.
Challenge: tidy your start-up
Time how long it takes from signing in until your computer feels ready. Choose one startup program that you recognise and do not need immediately, and disable it. Restart and time it again. Write a short note saying what you changed, the two times, how to undo it, and one startup program you decided must stay enabled, with the reason.
Knowledge check
6 questions. You need 80% to pass. Mistakes here are part of learning, and you can retry as often as you like.
Summary
- System Monitor and Task Manager show CPU, memory and disk graphs.
- A short spike is normal. Sustained 100 percent with nothing running is worth investigating.
- Startup applications run at sign-in. Disabling one stops it starting but does not uninstall it.
- Change one thing at a time and keep security software enabled.
- Clicking drives, swollen batteries, spilt liquid and physical damage need professional repair.
- Be wary of fake support pop-ups and calls, and back up before any repair.
Checklist: can you do these?
Marking a lesson as read does not prove you can do it. Skills count as demonstrated when you pass the quiz (not yet) and complete the practical tasks (not yet).
Related lessons
References and further reading
Official sources for details that can change between versions.
- Ubuntu Desktop help (Ubuntu)
- Windows support (Microsoft)