Lower FPS with upgraded system

So, I recently bought basically a new system.
Core i5 750
Gigabyte P55A-UD3
4 GB G Skill Ripjaw Series DDR3 1600 RAM
BFG OC Edition Nvidia GTX 260
Thermaltake TR2 600w PSU
Now, I expected this system to run almost anything I threw at it. I had the CPU overclocked to 3.6ghz but it did absolutely nothing for my FPS in any game, so I turned everything back to it's original specs. I thought that maybe it was just my video card but my friend and I put together a bunch of old spare parts:
Core 2 Duo 2.67Ghz
4 GB DDR2 RAM
Cheap Gigabyte mobo
XFX 8800GT Alpha Dog Edtion
This part is what pissed me off, the spare system was running things more smoothly than my brand new and quite expensive build. I read all sorts of forums and saw that my power supply at the time (Linkworld Generic 630w) was not quite up to par so I bought the one that I have posted and it had absolutely no effect on my FPS. I am at my wit's end and I will be really pissed if my system that I spent all this money on is actually worse than my old one. None of this makes any sense to me and any help with the matter would be greatly appreciated.
Thanks in advance.

Also in Just Cause 2 the benchmark test I get 27FPS on avg whereas the scrap computer got 34 using my GTX 260. Settings are all high as they go with everything on except SSAO and Anti-Aliasing at 4x. Res is at 1360x768.

ps I hope I don't get in trouble for double posting but I noticed my other post was in UK and Ireland forums... No idea how that happened.