You may have SATA connections running through a secondary chip. Look for a setting such as Onboard SATA/IDE Device and make sure it is set to Enabled.
For more specific help, we need to know your system specs. What motherboard do you have?
Its M4N78 ASUS motherboard, as for my other specs, 4gb ram, geforce GTX 260, and the processor is AMD phenom (cant remember exactly which). My PC is running on vista sp1 32bit