XP will not load after CPU installation

I had a perfectly good functioning unit with XP SP2. No issues since I built the unit 2 months ago. I bought an Athlon XP 2100 CPU, installed it, powered the unit and rec'd no response at all. I suspect the cpu is defective. I installed my Athlon 1200, power the unit, get the XP splash screen then the logon screen. I enter my password and the unit starts to load, but never completes, it just reboots and starts over again, post, XP splash screen, logon screen, enter password, then the unit reboots itself again. The reboot happens right after I enter my password. Keep in mind I had no issues before installing the XP 2100 CPU which I bought used.
When I login using the last known good configuration, I get just my wallpaper and no desktop.

I login under safe mode and the unit functions fine, but is limited due to being in safe mode. Something got damaged under my profile, OS? Memory?
Any thoughts?

 

Did you try a System Restore in Safe Mode?

Go to Start - All Programs - Accessories - System Tools - System Restore to access the System Restore wizard.

Note: When restoring a system in Safe Mode, an automatic "UNDO" restore point will NOT be created and will not allow a restoration to the current state if you wish to undo the system restore.

 

Will do and keep you posted!

 

The problem tuned out to be the CPU fan. After I installed my CPU, I did not align the fan properly and it was over heating cusing my unit to reboot.

Thanks for the system restore tip.