I've installed Crysis 2 once on my laptop, played it for a while, decided I'd play it on my desktop instead. I succesfully deactivated Crysis 2, installed it on my desktop PC, put in the serial key and it says "The serial key you entered is invalid."

What's with this? I'd really like to be playing Crysis 2 now, instead of checking up why it's messing up on me. EA/Crytek could you please let me play my game I payed for?

Talk to the retailer who sold it to you.

or you could file a lawsuit with the company that sold it to you. they are pretty easy to win if you can prove that the product never worked.

i filed a lawsuit with steam for selling me faulty download of STALKER call of pripyat and ended up with a $80 steam gift card.