Thunderbird stores profiles the same way Firefox does.
Navigate to the following address on the slave drive:
Drag the profile folder (it's in the form of "xxxxxxxx.default", where xxxxxxxx is random numbers and letters) from the slave drive to the same location on the host drive. Your profile (and presumably all your emails) will now be on the host OS. I've done it with Firefox profiles before, but I assume it works the same way with Thunderbird. I checked Thunderbird on my netbook, and inside my profile folder (if you go deep enough) there is a small file named "Inbox" (I only have 2 emails in my inbox because I only used the program once).
Let me know if this works for you.