Alrighty, I think it is you RAM. I have DDR (PC3200) and You have DDR2 (PC6400 or similar) Check these scores out:
first he blindly appointed its the multiplier after a screenshot of CPUz indicating 1.6GHz, they saying its your RAM.
If you are not 100% sure, do not come to your conclusion so quickly. You are just going to confuse the problems he is having and could end up spending needless time on something completely wrong.
1.6GHz is not a bottleneck, my Q6600 slows itself down when playing World in Conflict to 1.6GHz from time to time.
You can have everything else working perfectly on 2D with the wrong driver of your NVIDIA 8800GTS 320MB, but you won't score 10FPS in 3D.
The RAM mentioned as above. I don't think the RAM is faulty. But if you only told the RAM to run at a certain ratio to the CPU Frenquency (FSB) then you are limiting the RAM Speed. Or having the RAM speed on Auto, the BIOS usually select 200 or 166 where your RAM is capable of running 266 / 300 / 333 / 366 / 400 being a PC2-6400. But slow RAM speed does not effect your in-game performance, it will only increase your game's LOADING speed.
I'll get some advise else where in the mean while
Best of luck