While browing the web or changing the folders, I often get an windows explorer error message saying it has to be closed. Sometimes it simply hangs and you have to reboot the system. How to fix this error. Thanks for your help and time.

I would suggest first doing a defrage then a checkdisk and see what happens then. The defrage can be found on the Start menu. In xp is in Start -> All Programs -> Accessories -> System Tools -> Disk Defragmenter

Then checkdisk you will need to google for the appropriate command line.