A few weeks ago I got myself a tablet PC Toshiba Portege M205 on ebay. Pretty cool thing. Had a few issues like dirty screen and 10 missing screws, but I managed to make it work.
The longest it took me was finding a tablet (Wacom) driver for it. Finally got it from the Toshiba web site, for some older model and OS, like Windows NT4 or something. So far works ok, however it lacks some unique features like signature login, character recognition, etc.
I tried finding an OS for it, read a lot of MS information pages, and finally found out that MS does not sell Tablet edition separately from hardware. Which means, the only option to get the tablet edition is to get the original Toshiba dvd. Ha! - interesting. The last one I saw on ebay was sold for about $60. Which is unsatisfactory.
The only 'other' way to get it is through MSDN :) which I'm being helped right now with.
Anyway, recalling how long it took me to install the current OS, i don't plan to reinstall Windows on it again any time soon.