I have mostly gone to forums from Google searches in the past, and found help for my computer problems over the years. I usually don't sign up and post my solution if I find one, but this time I did. Hope this helps someone with this similar problem, since it seems so elusive.
I was getting the same problem with my newly build computer, and I didn't have any IDE drives, only SATA hard drive, and 2 SATA DVD drives. I tried switching the hard drive to be first in the boot order, and also tried putting it as Device 1. Both didn't fix the boot error. I then noticed I had some external hard drives that were plugged into the front USB connectors (they were plugged in when I installed Windows Vista Ultimate SP1 on the hard drive). I unplugged them and sure enough it fixed the problem, good Ol' Windows must have cached them as the boot device, or something else. Anyways, when I booted successfully, I shut the machine off, and plugged the USB drives back in, and rebooted. No problem now, and I don't need the Vista DVD in the drive to boot anymore.
Hope this solves everyones problem with this dillemma. Good luck!!!