Hi!

I have a Compaq Presario 5900T with Windows 98.

Last week my computer suddenly started to reboot by itself. It happens all the time. First after running 5-10 minutes and since yesterday, directly after the start-up procedure has ended. The computer works fine in safe mode. There are no warnings or error messages.

I have not added any hardware since I bought the computer 4 years ago and I have not installed any software recently.

I have reinstalled Windows several times, even formatted the harddrives before doing it, but it does not help. I have also turned off all programs that are auto-started and vacuum cleaned the power supply through the cooling "grille". Nothing changes though. The computer does not work in the normal mode and works fine in the safe mode.

Does anyone know what could be the problem or how I could isolate the problem?

Try updating the video drivers or replacing the video card. Since the PC does not reboot in Safe Mode, then that rules out an overheating problem so the problem is definitely software related. Typically related to the video card but possibly another installed PCI card.