I use steam quite a bit, but not enough to know the answers to either of these.
a)Does the retail box version of HR on the PC require steam validation?
b)Its impossible to unregister a game that requires Steam, right? Say if you wanted to sell it or something? You only get one code and its permanently locked to your account, correct? Just asking cause my copy of New Vegas is sitting around collecting dust and I'd like to ebay the shit out of it.
No idea on A, but as far as B, I believe that's the case. There are sites for selling Steam accounts out there, though.