Creative=Problem
Seriously, creatives cards are so finicky with the weirdest stuff, it just doesn't make sense why.
This was actually one of the issues i was having with the X-FI Fata1ity. Pull the plugs on the Sata drives and the weird sound would tone down significantly. (which would seem like a power related problem, but reguardless of the PSU used or Motherboard, it still did it in different tones or pitches)
Have you tried maybe slapping the creative card in another slot.
change the SATA power plug to a different one.
Is the creative card making the sound specifically, or is it the sound coming out of the speakers. Is the sound coming from somewhere else?
Is there anything else sharing the cable that powers the HD?