The guy who said to disable hardware devices untill it stops locking up is on the right track. You have tried all the driver stuff so I would guess bios or hardware. You should be able to backup your original bios to a floppy disk. If its hardware, diabling the onboard sound in bios, if possable might work but of course no sound. Another possability is bad sectors or scratches on the hard drive. run a checkdisk on your c: drive with all advanced options and see the results.