If you did not disable message synchronization in Thunderbird, and you get an error message that says "No space on local drive C," first go into "Account Settings" and, in the "Synchronization and Storage" tab, disable message synchronization for the account.
After you have disabled synchronization, you will need to clear out at least one folder that has filled up. Open a remote desktop connection to winterm, be sure that you are not logged into Thuderbird, and choose "Start -> Computer -> Users -> yourloginname -> AppData -> Roaming -> Thunderbird" and remove everything inside the Thunderbird folder.
If you still need to clear more space, go back into the AppData folder and, this time, choose "Local -> Thunderbird -> Profiles -> randomNumbers&letters.default* -> Cache" and remove everything in the Cache folder.
* e.g. 4xf69dze.default
Tuesday, 23-Aug-2011 09:51:34 PDT