How do I find out who is right ?
Try it on a laptop cooler see if that stops the problem.
Seriously PCs shut down for a number of reasons heat being a prime example 3 and a half years is a lot of dust build up.
2. driver conflicts
3. Spyware / viruses
4. memory problems.
5 corrupt files / hard drive errors
6 lack of space on HDD.
1. clean out grills on laptop
2. check for updated drivers
3. scan for spyware and viruses
4. run memtest click here
5. Disble Autoreboot
Open System Properties via Start > Control Panel > Performance and Maintenance > System
[ System Properties may also be opened using the WinKey+Pause key combination ]
Select the Advanced tab and then click Settings in the Startup and Recovery section
In System Failure section, clear the checkbox next to Automatically Restart
Click OK and OK to exit
Now you should be able to see the error message when windows crashes.
Post the message here for further help.
6. Clear out all temporay files and folders -- use Crap Cleaner click here