So uuhm, I'm getting this weird fps issue. It kinda jitters a lot and I don't think It's not steady enough to be from my GPU. I think my hard-drive is a major bottleneck.

I need a new HDD, don't I? :c
Phenom II X4 940 Black Edition @ 3.6GHz
Radeon HD 6950 2GB
8GB DDR2 RAM (I got this Phenom as soon as it came out, when it was still AM2+)
111GB SATA HDD
Can a slower hard-drive cause performance issues like that?