> I have around 20 foxuser.dbf on my machine.
> Which one should I delete?
You should delete the one that is being used by the instance of VFP that is crashing. If you don't know which one is it, you should probably start by deleting

* the one on Windows directory (winnt\system32)
* the one on in VFP directory (program files\microsoft vfp7)
* the one on the last project that you were running when VFP start crashing (e.g. dev\myproject)

Make backup of these resource files in case you need them later.