Computer help!

Hey, I wasnt sure where to post this but here it goes… A few months after purchasing my latest PC the CPU fan in it failed. I have replaced the fan with no problem at all but the problem is this… The original fan had a four pin connector on it which obviously connects to the motherboard letting it know when there is a problem. The fan I installed is much better but my PC doesnt think that the fan is there as it doesnt connect to the motherboard! Everytime for the past month I start my PC I get a CPU fan failure alert. This doesnt affect performance as the new fan works fine, Its just annoying as hell. Anybody encountered this problem/know what to do? I have cruised around the startup utility and BIOS but there doesnt seem to be a fan detection option. Please help!!!

Sneaky x