guardate cosa ho trovato la soluzione a questo post, la trascrivo qua in modo che possa essere utile a tutti. E' in inglese ma è facilmente comprensibile.
It's possible to move the location of a profile folder. This could be useful if you have a backed up profile folder somewhere on your hard drive and want to tell Thunderbird to use that as your profile. This section explains how to do this.
Shut down Thunderbird completely (File > Exit).
Move the profile folder to the desired location. For example, on Windows XP, move the profile from C:\Documents and Settings\[username]\Application Data\Thunderbird\Profiles\xxxxxxxx.default to D:\Stuff\MyMailProfile. If you are reading these instructions because you want to restore a previously backed up profile, this step isn't necessary. Just note the current location of the profile you want to restore.
Open up profiles.ini in a text editor. The file is located in the application data folder for Thunderbird:
On Windows Vista/XP/2000, the path is %AppData%\Thunderbird\
On Windows 95/98/Me, the path is usually C:\WINDOWS\Application Data\Thunderbird\
On Linux, the path is ~/.thunderbird/
On Mac OS X, the path is ~/Library/Application Support/Thunderbird/
In profiles.ini, locate the entry for the profile you've just moved. Change the Path= line to the new location. If you are using a non-relative pathname, the direction of the slashes may be relevant (this is true for Windows XP).
Change IsRelative=1 to IsRelative=0.
Save profiles.ini and restart Thunderbird.
Ciaoooo