I don't know if this is the same one, but Microsoft does offer SP2 for public preview - I'm running it at home. I don't have a URL handy, but I downloaded it directly from their site, without any special access.
Edit: Yeah, I looked at the URL - it's directly from Microsoft. Now, that WMP10 might be a bit more sketchy, I dunno, I know it's not part of SP2 right now.