winlogon.exe locking up my winXP

[Konig]

After booting up and working for a while the CPU utilization goes to 100%. I checked taskmanager and it shows that "winlogon.exe" is doing it. I've tried many things and ahe had no luck. It usually locks up when running Outlook. I have Office XP and installed service pack one when the lock ups started. It didn't stop. I'm now trying uninstalling MS Messenger.

Does anyone know what could be causing this?

Thanks in advance.