If your not finding any malware the symptoms you describe could be due to hardware or overheating problems caused by a failed processor fan, bad memory (RAM), failing power supply, CPU overheating, motherboard, drivers, etc. If thats the case then reinstalling Windows will not resolve the issue.
When was the last time you cleaned the inside of your computer? Open your machine and make sure the fans are working and the heat sink on the processor is not blocked with dust or debris. Remove the CPU's cooling unit and clean the fins on the heat sink that sits under the CPU with a can of compressed air. Dust restricts the airflow and prevents proper cooling. You can also remove the cards, RAM modules, clean and reseat them. Check your connections and fans to make sure they are working properly and monitor the temperature. If the computer is overheating, it usually begins to restart on a more regular basis.
In Windows XP, the default setting is for the computer to reboot automatically when a fatal error occurs. If that fatal error only occurs when you're shutting down, the system reboots automatically and you should be able to see the error by looking in the Event Log. An alternative is to turn off the automatic reboot so you can actually see the error code when it happens. This is a Blue Screen of Death (BSOD).
To change the recovery settings and disable automatic rebooting, do this:
1. Right-click on My Computer and select Properties
> Advanced tab
2. Click the Advanced tab.
3. Under "Startup and Recovery
" click on the "Settings
" button and go to "System failure
4. Make sure "Write an event to the system log
" is checked and
that "Automatically restart
" is UNchecked
5. Click "OK
" and reboot.
Doing this won't cure your problem but instead of restarting you will get a blue diagnostic screen with information displayed that will allow you to better trace your problem.Download and run Motherboard Monitor 5
. If Motherboard Monitor's seems to be reporting high temperatures for your CPU check to see what your max CPU temp is from here
There are suggestions for troubleshooting power supply, video card, CPU, RAM, MB and hard drive here
Try Microsoft's Online Crash Analysis
- The Windows Memory Diagnostic tests the Random Access Memory (RAM) on your computer for errors. The diagnostic includes a comprehensive set of memory tests. Also see Memtest86+
Check for updates to your drivers
with a free Driver Scan
Check your computer's Disk Health here