So what happened was, I bought a new comp. installed Windows 7 on the HDD inside and everything was fine.
Then, I added another HDD, but I notice it operates quiter, so I decide to make that new HDD my main drive.
So I chuck in the Windows 7 disc, get my BIOS to boot from it, install Windows 7 on the new HDD, while leaving everything on the hold HDD completely intact but from now, it will be used as a secondary storage drive.
I go into BIOS, and tell it to boot from the NEW HDD from now on.
However, it takes me to that "Windows Boot Manager select default operating system" screen you all know so well.