I cannot log off, or I keep getting emails, because I am over my profile quota.

Please see:

All About Profiles in Windows

for information about your Windows profile and how to keep it under quota.

The most common cause of being over quota is your Firefox browser cache. For important files on your desktop or in your My Documents folder, it is recommended to store them in your home directory (H: drive under Windows) and have shortcuts to them on the Desktop/My Documents.