You can try a repair install of Windows XP. Might be the easiest way to deal with this.
You will need a Windows XP disc for this, not a restore or recovery disc. Not sure what Dell did for that system.
Here is a link to instructions on how to do this:
http://michaelstevenstech.com/XPrepairinstall.htm
Read the warnings and back-up your data.
Pauldo