Don't get upset at a member trying to help. However due to the fact you can boot with the 320 proves that you have the correct drivers for the drive and don't need any SATA drivers.
I have seen this problem before, it's a fairly odd and very confusing and random problem. You have boot files on multiple hard drives. How exactly did you install the OS, did you install it with all the hard drives plugged in, or just one? Also what is the drive letter of the windows drive?
The first thing I would try removing all but the 320GB HD, and inserting your windows CD. Go into the repair console and once you are at the prompt run "FIXBOOT" and "FIXMBR". This will rewrite all the necessary boot files to your 320GB drive. For whatever reason some of them could have been written to a different drive, seen it happen many times.
Tell me how this goes