File Explorer Slow-Not Responding WinXP

Windows XP Professional SP1, and all the latest patches.

Compaq EVO N1000V P4 2GHZ 512MB

We have a Windows 2000 based network, and use mapped drives due to some of our applications. When I am connected to the network Windows File Explorer works fine. But when I disconnect from the network, even after a re-boot, if I open up windows explorer then click on or attempt to expand, My Computer, explorer locks up. I also see this when using MS Office when attmepting to
open a file. Any ideas? Thank you!

Al Durham