Read http://forums.cnet.com/7723-6122_102-569818/getting-ready-to/?tag=contentBody;threadListing to read about canned air and replacing heat sink compounds.
Registry cleaners tend to create issues here. Odd choice.
I've been running XP Pro/SP 3 for a couple of years without any problems. A couple of months ago I started noticing a tendency for the machine to reboot at inappropriate times: like running a virus/adware scan, or trying to write to CD-RW.. I didn't bother trying to figure it out when it was only an occasional incident, but now it can happen every couple of minutes no matter what I'm doing. I have noted several error codes including 15, 7000, 7023. The explanation claimed problems with Removable Storage Manager, Remote Access Manager, NVIDIA, among others. There seems to be a tendency for databases of drivers to get corrupted, if I am reading these messages correctly.
I tried restoring to an earlier system date. That helped for anywhere from 1 day to 1 week. I tried using the repair feature of my XP install disks, and that didn't seem to help. I ran Revo Uninstaller Pro to get rid of junk files, used a registry cleaner, and defragmented the drive.
I am running it in Safe Mode as I write this, and that works fine. It's not a solution, though, as there are many features I can't access in Safe. I realize I may need to completely reinstall the O/S, but I'd like to have some understanding of why this is happening. Can anyone help?