|Safe mode lets you start when a program or hardware driver is corrupted. It does not load the faulty component.|
Process of elimination.
The Benefits of Windows Diagnostic Startup Mode
How to use MSCONFIG in Windows XP
Disable all services and startup programs using the msconfig tool. See if you still have the issue & if OK, then start them up in sequence to troubleshoot the device or driver that is causing the issue.
Click on the "Services" Tab, put a check in "Hide all Microsoft Services", then click "disable all"
Click on the "Startup" Tab, click "disable all"
Reboot and test.