windows xp sp1
40Gb HD
Duron 1400
512 Mb RAM

I have a problem with a PC which reboots during startup of XP SP1.

I have tried safeboot, and any option I use, the files get as far as
C:\Windows\System32\Drivers\Mup.sys, then a PC Reboot occurs.

I have tried a repair install, a message returns advising that a previous version of windows cannot be found.

Last update made to this PC was to configure Outlook Express 6.

Can anyone help.