Well there's RC1, RC2 then OEM. (OEM is what will be given to OEMs, so it's the same as the retail box version)
Basically, RC means it's most likely done in terms of the features, design, programs that will come with it. From now on, they're mainlly going to focus on fixing bugs.
BTW, I know you guys are probably joking, but XP is actually very stable for a BETA product. I haven't had one crash or error since I installed it, and the only problem is my sound card, but I doubt that's MS's fault. I still don't recommend running it on its own until it's final, but dual-booting it to see what it's like is fun.
