Here are my hardware specs:

XFX Ultra 790sli MB
Intel Quad-Core Extreme (Yorkfield)
4gbs of 1600ddr3 Memory running on XP pro
1gb Nvidia video card

My question is as stated in the subject line:

Will adding more hard drives and moving wow folders to said drives speed up performance?

Currently I have decent frame rates and little lag to speak of except in Dalaran. I can move all 5 shamans around with relative ease -- occasional glitch now and again but nothing show stopping. Last night I tried WG (winterlag) for the 1st time and I was shocked that I could barely move, let alone participate. Is there a chance that adding the additional drives will boost performance?

Thanks for your help