Since Mozilla released Thunderbird 2.0 Alpha 1 I decided to put together a portable version for the several requests that I had. If you are looking for a more stable version John Haller has it over at PortableApps.com.
All you have to do is download the Portable Thunderbird 2.0 Alpha 1 file below. Then you unzip the file and browse for the file PortableThunderbird.exe. Just execute that file and you will be running Thunderbird 2.0 Alpha 1! The profile is kept with the PortableThunderbird folder so you don’t have to worry about messing up your other profile and the uninstallation process is simple, just delete the folder!
I haven’t really had time to test the portable version so I am not sure how stable this is.