Running from a USB drive - Thunderbird
From MozillaZine Knowledge Base
Can you run Thunderbird from a USB drive (keychain drive)? The short answer for now is no -- at least, not easily. For possible workarounds, search the MozillaZine Thunderbird forums for "USB drive" (both words, without the quote marks).
Support for USB drives seems to be part of the Thunderbird development vision for 2004, however, so stay tuned.