Computer Troubleshooting II – SS2 Computer Hardware & GSM Repair Lesson Note (First Term)

Computer troubleshooting is the step-by-step process of finding and fixing faults that appear while a computer is running or loading Windows.

• Last lesson: POST and beep codes, the faults that happen before the computer starts.
• This lesson: the “daytime” faults, which happen while you work or while the desktop is loading.
• Common faults: boot failure, overheating, the Blue Screen of Death and freezing.
• Good habit: stay calm, because many faults are the computer protecting itself from permanent damage.

Behavioural objectives

By the end of the lesson, students should be able to:

1. describe the symptoms and common causes of a boot failure;
2. explain why a computer overheats and how to prevent it;
3. state what the Blue Screen of Death is and how to read its Stop Code;
4. describe Safe Mode, System Restore and Event Viewer;
5. match common computer faults with their quickest fixes.

What is a boot failure?

A boot failure is a fault in which the computer passes POST (no beeps) but gets stuck and cannot load the operating system, such as Windows or macOS.

What are the symptoms of a boot failure?

• Error message: “No Boot Device Found” or “Operating System Not Found”.
• Blinking cursor: a white underscore (_) blinking on a black screen.
• No beeps: the hardware passed POST, so the fault is in the boot stage.

What are the causes of a boot failure?

• The wrong “door”: a USB flash drive or DVD is plugged in, so the computer tries to boot from it instead of the hard drive.
• Loose cables: the SATA cable (the “umbilical cord” for data) inside the computer has wiggled loose.
• Corrupted software: a recent update or a virus has broken the startup files.

How do you fix a boot failure?

1. Switch off the computer.
2. Unplug all USB drives and remove any DVD.
3. Restart the computer.
4. If it still fails, open the case and check that the SATA and power cables are firmly seated.
5. If the cables are fine, suspect corrupted startup files and use the Windows repair options.

Why does a computer overheat?

A computer overheats when heat builds up faster than its fans and heat sink can remove it.

• Everyday comparison: you cannot run a marathon in a thick sweater, and a computer cannot work well when it is too hot.
• Heavy use: gaming and watching videos make the processor produce more heat.
• Self-protection: the computer shuts down suddenly to avoid permanent damage.

What are the symptoms of overheating?

• Sudden shutdown: the computer switches off without warning.
• Loud fans: the fans spin very fast and sound like a jet engine.
• Hot body: the computer feels hot to the touch.

What are the causes of overheating?

• Dust: the main cause. Dust clogs the fans and acts like a blanket that traps heat.
• Blocked airflow: using a laptop on a soft bed or pillow covers the air vents.
• Dried thermal paste: this paste sits between the CPU and its heat sink (the metal part under the fan). Over the years it dries up and stops moving heat away.

How do you prevent and fix overheating?

• Clean the dust: blow it out with a can of compressed air.
• Use hard, flat surfaces: always place a laptop on a table or desk.
• Clear the vents: keep the air vents free from walls, cloth and paper.
• Replace dried thermal paste: a technician removes the heat sink and applies fresh paste.

What is the Blue Screen of Death (BSOD)?

The Blue Screen of Death (BSOD) is a blue error screen that appears when Windows meets a fault so serious that it must stop and restart.

• What it shows: white text on a blue screen, such as “Your PC ran into a problem and needs to restart.”
• What it means: a system crash. The computer stops everything to prevent your files from being corrupted.

What is a Stop Code?

A Stop Code is the error name, written in capital letters, that tells you the reason for the crash.

• Where to find it: usually at the bottom of the blue screen.
• Example: MEMORY_MANAGEMENT points towards a memory (RAM) problem.
• Example: DRIVER_IRQL_NOT_LESS_OR_EQUAL points towards a driver problem.

What are the causes of a BSOD?

• Bad drivers: the software that tells the hardware how to work is faulty or out of date.
• Faulty RAM: one of the memory sticks is physically failing.
• Hardware conflicts: a newly plugged-in device, such as a printer or camera, does not work with the computer.

How do you fix a BSOD?

1. Write down the Stop Code before the computer restarts.
2. Let the computer restart, since a simple restart often fixes a one-time crash.
3. Search for the Stop Code online, for example on a phone.
4. If the crash keeps happening, update the drivers.
5. Unplug any newly added device to check for a hardware conflict.

What are the advanced diagnostic tools?

There are three advanced diagnostic tools in Windows: Safe Mode, System Restore and Event Viewer.

What is Safe Mode?

• Meaning: a way of starting Windows with only the basic drivers and services.
• Use: if the computer works well in Safe Mode, the fault is a software app or a driver, not the physical hardware.
• How to start it (Windows 10 and 11): hold Shift and click Restart, then choose Troubleshoot, Advanced options, Startup Settings and Restart.
• Choice: press 4 or F4 to start Safe Mode.

What is System Restore?

• Meaning: a “Time Machine” that returns Windows settings and programs to an earlier restore point.
• Use: go back to a day when the computer worked well, for example “last Tuesday”.
• Effect: it undoes recent system changes and does not delete your personal documents.

What is Event Viewer?

• Meaning: a “hidden diary” inside Windows that records errors and other events.
• Use: it shows what happened at the time of a crash.

What causes a computer to freeze or lag?

A freeze is a fault in which the computer stops responding, for example the mouse will not move.

• Too many open programs: they use up the RAM and processor.
• Stuck app: one program stops responding and holds up the rest.
• Quick fix: press Ctrl + Alt + Delete, open Task Manager and close the stuck app.

What are the common computer issues and their quick fixes?

The table below matches each fault with what you see and the quickest fix.

Evaluation

1. What is a boot failure? Give two symptoms.
2. List three common causes of overheating and state one fix.
3. What is a Stop Code, and where do you find it on a BSOD?
4. Explain what Safe Mode and System Restore do.
5. A computer shows “No Boot Device Found” after a flash drive was left in. State the quickest fix.

Assignment

Next time your phone or laptop gets very hot, turn it off and let it cool for 10 minutes. Then write down two likely causes of the heat and whether it ran faster afterwards.