Well I had this problem. You can either move the pin crap, (I think that's what it's called.. i forgot ;x lol) on your motherboard or you can push F10 to get in the BIOS and look for a setting there.
Sometimes, the motherboard will automatically detect things like that.
Windows 7 Pro x64
AMD 965 Black Edition 3.4GHz
ASUS Crossfire III
Corsair 650 Watt
Sapphire ATI 5770
500GB Samsung*2 | 150GB VelicoRaptor 10K HDD
C# Programmer+Web Programmer