I noticed that Office 2007 makes a new category in Event Viewer: Microsoft Office Sessions.
Example:
ID: 6, Application Name: Microsoft Office Outlook, Application Version: 12.0.4518.1014, Microsoft Office Version: 12.0.4518.1014. This session lasted 2766 seconds with 1080 seconds of active time. This session ended normally.
I wonder if CCleaner could clean these event logs?
james