What is your year and model?

 

Darn. I was under impression that this forum knows everything

 

its a 2005 c230 kompressor sedan
the thing is that the second key i have is for another c class
please help me resolve this. the dealer said it would cost a lot of money

 

So you have a key from other car and you wonder why it is not working on yours?
I am afraid your only option is pay dealer for new key. Shop around as the prices can wary quite drastically. Having 2 dealers in 7 miles range I bought the key from the dealer 30 miles away, as I could combine that with other business and the drive save me over $100

 

so it has to be bought from the dealer?

 

Yes dealer only. As previously posted call different dealers to try and get a better price.
Also you will need to prove you are the owner so you will have to bring proof of ownership when you order the key.
Keys used from other cars will not work and can not be programmed to your car by a dealer.

 

thanks