Always have mirror turned off. It's most definately the exhaust effect, taking the fps down to low teens. Turning the visual effects to low kills that particular graphic effect & fps climbs again but a very large part of the games graphic effects goes with it. The moment I turn CEM off, the fps counter is back in the 40's.

It's got a very good chance of being the CPU, in all honesty - the CPU "feeds" information to the GPU to display; if the CPU is lagging behind, the GPU has to wait for the CPU to give it what it needs to display the frame.

A quick and easy test would be to run a program(s) that displays a graph of CPU usage and GPU usage. In times of low fps as you describe, I'd expect to see the CPU working at 95-100%, and the GPU load dropping a little - though the GPU load may not drop at all, depending on what's going on and what screen resolution you're running at.

Overclocking is inherently dangerous, but that's why I directed Houndstone to an overclocking beginner's site - I won't be telling him to "press del on bootup and whack CPU voltage to 1.4 and yer done" - like anything fun in life - if approached in the wrong way it can indeed be dangerous/costly. Done in the correct, slow and safe way, there's very little risk involved.

Took another screenshot with the task manager performance tab running.

Hmm, That doesn't prove much, tbh. With a quad core, windows would be sharing some of the work by default anyways, but seeing that one core running >90% tells me that it could well be the issue.

It's up to you really, mate - if you're willing to risk-it-for-a-biscuit, overclocking almost certainly would help - the other options are to buy a faster CPU or upgrade to Win 7.

The rest of the rig is definitely up to the task imo.

If you do decide to OC - read that beginners guide. Then read it again. Probably best to do it a third time before you even get into the BIOS. A friend who knows what he's doing on hand to help would be good - but as long as you take it slowly and try to learn rather than blindly follow instructions, you should be fine :)

Feel free to PM me if you need any help, whichever way you go.

Couldn't help but notice the clouds rendered in your low fps shot. Have you tried disabling them? They seem to be pretty demanding for my rig at least.

Not sure what I can add to help but my CPU is similar to your except I've overclocked my CPU, but you however have a much better graphics card.

Over all I'm getting reasonable results with my PC. The only big difference is that your using Vista. I managed to get a cheep Windows 7 upgrade deal through my work and have never looked back. Windows Vista is an abomination! Irt's slow and horrible.

Hope you get your issues sorted out