I installed Windows 7 Pro 32 bit (full) (ultimate is fine) but You can only use 32 bit.
Someone tell me I am wrong if you can install 64 bit, but I do not think so.
You will love 7 on there.
Good luck. Oh I bought another drive and installed and kept the factory drive on the shelf just in case I did not like the change.
So far the factory drive is on the shelf, and that was over a month ago! :-)