You need to do some basic troubleshooting to to diagnose this problem.
1. Go to Start/Run and type: eventvwr.msc and press OK. This will open
the Event Viewer. Click the Applications item on the left side. On the right
side, look for any "X" error messages that may be displayed. Double click
the error entry to see the details. The specific module causing the error
will be shown there.
2. Go to Start/Run and type: msinfo32 and press OK. Click on
Components/Problem Devices to see any hardware that may be having problems.
Click on Software
Environment/Windows Error Reporting to see any possible
conflicts and or error messages.
also you can try this:
Click Start/Run and type control userpasswords and click ok. Does this
open the
user accounts?
Also, is this a fresh install of XP and if so did you check hardware compatibility before installing XP on that
computer?
I hope this help!
spider