i have swapped cpu from i7 to an i5 on my mb, and got the activation nailed in Steam
the message was saying something like due to a "significant" hardware change, the activation blabla blabla..
the "significant" hardware change was just a cpu change! what the hell???
ps: i have other games installed with my steam account (ARMA2 OA, Mafia II etc) havent launched those yet since i have swapped cpu, i blieve those activations will be nailed as well!