New SATA HDD not recognized in Windows?

I have an exiesting SATA 2 HDD in my system. I just bought a Samsung 200GB SERIAL ATA HD 7200/8MB/SATA-3G HDD which I ume is also SATA 2 based off the throughput speed. It is recognized in BIOS, but not in windows. Does nayone know what is going on? Does it matter if I mistakenly got a non SATA 2 HDD, w/ a MOBO that is designed for SATA 2. Even though BIOS sees it?