I go in to the view menu toolbars only thing checked in there is status bar. then view menu view message body as original HTML is checked.
Not sure where I did this but turned off the extra tool bars so I just have the tree view with the folders and the list view of messages like outlook express.
Out of the box Thunderbird has a today pain and some tabs and a few other fluttery things open. Tabbing threw them is time consuming and some times you can get stuck in a window element. So I just turn off every thing I can. There is a chat section to disable also unless one uses it.