Do the following steps.
- Click Start Menu
- Type eventvwr into the Search programs and files
- Expand Custom Views
- Click Adminstrative Events (you may get a dialog saying access is denied to security events, just ignore it)
- Check for reoccurring errors
If you need help determining what causes an error, copy and paste part of the error into Google, or copy and paste the full error into this thread. We should be able to track it down.