As of September you can download and try out a 360 day preview of Windows XP.
http://www.microsoft.com/windowsxp/64bit/evaluation/upgrade.mspx
"Keep your friends close, but your enemies closer."
-The Godfather-
Too bad I don't have a 64 bit processor. I wonder how many people actually do.
On a similiar note, my brother-in-law is working with Microsoft and has access to the developer's area of some Microsoft website, and I can actually download a beta version of Longhorn. If I only I had room for another computer in my apartment I could install it on another computer.
Well, even if I had 64-bit processors and they were demo'ing Windows 64-bit, I'd use my free and fully functional open source OS, which have had 64-bit capabilities for years now :)
Until all games come out with Linux compatible versions, I'm stuck with windows.