I have a MINT condition game for sale. Its LEFT 4 DEAD for the PC. First $35 takes it. This is one of best games of the year from Valve. I only played twice (just don't have time for it.) You must pickup (I live out by Chaska and work in Golden Valley) and No lowballers!
I don't think you can sell it off, if you played it online, you had to sign up for Steam and that game is then tied to your account.
Indeed, i would check steampowered.com in the help section, see what they recommend for this situation.
Bingo. if it's been tied to a steam acct, then it's tied to it. and being a valve game, you have to tie it to a steam acct to play it. which means.... You can't sell it. Valve/Steam don't allow for the sale or transfer of games. only way to do it would be if you sold the whole acct it's tied to, and all the games in it.