I installed everything, the system POSTed correctly and I entered BIOS:
My HDD was not detected in CMOS in IDE/SATA Channel 0 in where I plugged its connector into the MoBo. Troubleshooting, I tried plugging the connector into a different SATA port on the MoBo(that I knew worked since it recognnized the ODD that was in it before), tried another SATA port, tried another SATA power cable that came with the PSU, tried the ODD's power cable, tried the original 0 port with the other SATA power cable and then 0 port with the ODD's power cable. The only thing I didn't try was plugging the SATA MoBo connector into one of the Gigabyte's GSATA2 (SATA 3Gb/s connectors, controlled by GIGABYTE SATA2) ports, but I don't think that should be a problem since it says that the SATA3 (SATA 6Gb/s connectors, controlled by AMD SB850) ports are compatible with SATA 3Gb/s . (See page 27-28 of the users manual)
I don't know what's wrong, I think it might be defective or something. Any advice or help would be greatly appreciated. I ordered the HDD from anitec.ca on the 16th, it got invoiced on the 17th and delivered on the 22nd so I think I have 2 days to RMA it (I'm not sure which day they start counting it from).
Edit: Forgot to mention that even looking at it when the system is on, it didn't appear to be doing anything (didn't look like it was spinning, no noise).