GUID BAN-COD4

Could anybody help me out? I got GUID banned , and can someone help me to change my GUID, or fix it at least?
I will be very happy if someone can help me!

~Martin

Change your Cod4 serial key and you can play on Gameranger and some other clients but you can't play in Steam if you get the serial key from some keygens!
Because Steam will only accept the purchased serial keys if it's not in use in any computer!