Computer detects HDD in BIOS, but not after I boot up

So I have yet another problem.

In my computer build, I installed both a 128 SSD and a 1TB HDD. When I got the computer to start for the first time, I left the HDD unplugged so that I could boot my OS from the SSD. The plan was to get everything up and running, then go back and connect the HDD.

I have the HDD plugged in now, but when I go to check it on my computer all it shows is the SSD. I've gone into BIOS and saw that it recognized that a Western Digital Caviar 1TB hard drive was plugged into my SATA3 port, but I can't seem to store anything on it or access it at all otherwise.

Any suggestions?

Thanks!