Occationally suddently my PC stops and displays: Windows Protection error. You must restart your computer. Thereafter the PC is dead and I have to cut power and then power on again to restart. What should do to prevent this from happening.

There are so many possible causes comment is impossible on so little information. If there is no pattern to this (i.e. particular software you were using or particular circumstances leading up to it) go through the tips on the homepage link on this response to start with, especially point 6 since you have 640 Mb RAM. Also remove anti-virus and firewall software and see if that makes any difference.

Are your cpu clock settings correct? This error occures with amd chips if they are set to run to fast. Enter the bios and make sure the cpu settings are set to auto. This will give you a starting point. If you want a little more speed move it up slowly until the error occures then knock it back down to the last setting that was ok. It is recommended to leave it on auto though. ASE