...then something is wrong with the WinXP install.

The most radical approach would be to reinstall XP, which *should* keep some user settings but not all. So last resort only.

If you can get to Windows, you can use msconfig.exe to disable startup services.

I guess you could also try to fudge some of the INI files (win.ini, system.ini); but that's pretty dangerous as you risk breaking more thigns if you don't back them up.

It could maybe be the hardware too - you can try using the memtest liveCD (boot in Linux by itself, then scans the RAM for physical issues). If the machine has extension cards, you can remove them to see if it prevents the BSOD.