I recently got a new hard drive so I'm now reinstalling Windows 7 on my Lenovo ThinkPad X200 tablet PC. I could have cloned my old hard drive, but I generally prefer the clean installation method. It gives me a chance to do a bit of housekeeping.
Thanks to a fast Internet connection, I was up and running in a very short amount of time. I used my Windows 7 DVD to install the OS, then I used a combination of the Lenovo System Update and the Microsoft Windows Update to install all the necessary drivers and system software.
If you're still running XP or Vista on a tablet PC, then you really should try Windows 7. I've found that this OS offers some great features for the tablet form factor. If you really need XP or Vista, then simply create a second partition and test drive Windows 7 on that second partition. If you're running out of space on your hard drive, then do what I did: upgrade to a larger HD.