For the prefetch files, try setting CC to use 'Normal file deletion' as opposed to the 3 pass. There may be a bug or similar with that feature and this will help isolate the problem.
For the reboot problem, more than likely this is related to XP's auto restart option which is enabled by default. When windows encounters an error, the system will reboot. Your only clues to figure out why are viewing the event viewer to see what the problem was and/or disabling the auto restart so that your presented with an error dialog instead. Some times you will get a blue screen error if its hardware related.
Here are instructions
Right click on "My Computer"
Select Properties.
Select Advanced Tab
Click on Setting under ?Startup and recovery?
Then uncheck "Automatically restart"
Here is a site with detailed info: http://somethingcomputers.com/tutorials/xp...r_reporting.htm