PC freezing up constantly

User has Compaq DeskPro EP 466 MHz w/3GB hard drive, NT 4.0, 64 MB ram and not too many apps installed. Frequently user will be working on any application and before she can save the pc freezes and the only way to reboot is turn off pc then all information is lost. We have upgraded to SP5, uninstalled and reinstalled Office2000 and everything except reformatting the hard drive (which might be next). This happens once a week then increases to two/three times/day. Are there any troublshootingideas with the pc that I haven’t tried? This pc is about a year old and she wants to take a 2 x 4 plank to it right now. We could never recreate the problem in our area when trying to work on it. Any ideas would be helpful and thanks.