I just bought a new PC with an Intel DG31PR Motherboard and a Seagate
320 GB ST3320613AS SATA2 drive. Everything was working fine, so I
decided to add a second SATA2 drive. I bought a 750GB Seagate
ST3750330AS and plugged it into the second SATA port on the
motherboard but it was not recognized by the BIOS. Finally figured out
that the drive only works in port3 and not ports 2 and 4. Could this
be a faulty motherboard, or is there some other possible problem here?

Ed