At the moment on my current setup I'm running ( 4 x 1024mb ) of Corsair XMS PC6400C4 DDR2 800 memory, with my voltage set at 2.0v and my timings at 4-4-4-12 and a 2T command rate. I have been able to achieve an overclock of 3600mhz with my system and can't get it stable past that point. Could my memory be holding me back and if so what would you recommend I switch too.

What do you have the divider set at?

If at 3600 your ram is at 800 then you must have the divider at 1:1. That ram should be able to go higher than 800... you might have to loosen the timings or up the voltage though.

My divider is set at 1:1 , so I'll try to loosen timings and see what happens. Thanks

Your memory should be able to easily handle 2.1v to 2.15v, don't be afraid to go up a little bit with the voltage to get things to run smoothly.

 If that doesn't help, you might have to bump up your voltage slightly to your chipset and other various options. Just make sure you don't get to crazy with the voltages

I bumped up the memory to 2.1volts and loosen my timings to 5-5-5-18 . I was able to acheive a 3800mhz overclock and am stable for now still doing some testing. Thanks for your help.

 Make sure you're running memtest and a cpu stress tool (such as orthos or prime95) to make sure they are indeed 100% stable. Having a unstable oc and unstable ram can give faulty installations and a corrupted OS. So make sure they are all 100% stable.