Can't recognize 2 drives

[007rex]

I was trying to upgrade to a larger drive -- had some problems so I tried to return to the previous configuration which was an 80 Gig "C" drive and a "120 Gig "D" drive. Neither drive was detected and that is what the Bios shows. When I hook up the C drive alone everything works great (except for the things it looks for on the second drive). When I hook up the second drive it is detected by the Bios fine. Both drives connected -- no detection. I hooked as master and slave and as cable select -- no difference. I swapped cables and also IDE connections. No difference.

Both are WD drives and I ran the diagnostics on both and both report as Good.

I am running Windows XP Pro sp-2. Intel P4 HPT chip.

Any suggestions as to why it does not detect the drives when both are connected? I am now suspecting Power supply or Motherboard problems.

Thanks,

007Rex