System only renders 3,22 GB usable out of 6GB of RAM - Windows 7 x64

Hey Community.

I have a problem. I installed a new PSU not long ago, and since then out of my 3 x 2 GB RAM, Control Panel\System and Security\System tells me this: Installed Memory (RAM): 6,00 GB (3,22 GB usable)

Why does it do this?
Notes
* The reason for having 3 x 2 GB RAM is because I had 4 RAM sticks from the start, but one broke over 1 year ago. It has been working fine with 3 x 2 GB sticks tho for over a year.
* My previous PSU broke not long ago. (2-4 weeks) It was probably because it had overheated (due to lots of dust inside the computer)
After replacing it with a new one this started.
* Again, 3 x 2 GB worked before the new PSU. I don't know if it's PSU related or what it is.. But I need a solution ASAP please.

I want to for example start playing Planetside 2 again. But it requires about 2 - 2.5 GB of RAM to run.
Buying new RAM's is out of the question.

Help!!!

OK. I have to update you on what just happened...

So since I only had 3,22 GB RAM now, I decided to troubleshoot my motherboard.
I had an previous motherboard that I thought broke on me (so I bought a new one) but it was one of the RAM sticks.
I plugged in all the parts into this previous motherboard and try starting.
To my surprise, it didn't boot up at all. So I looked at the CPU and I noticed one of the pins and been severely bent.
I try bending it back, but it had been bent to much that it actually broke off.
I got an AMD Phenom(tm) II X4 970 3,5 Ghz. If you go straight diagonally from the where the arrow points on the CPU to the other side, that's the one.
Also.. Another weird thing.. Pluggin it back in I happen to find my old RAMstick that broke some while ago. I decided what the hell lets plug it in. AAAND to my surprise it's still working. I guess it was the motherboard that was damaged...

So NOW, I got 5,97 GB Total Physical Memory that is usable out of my 8GB Installed.
I guess because of the bent pin (now broken pin) (surprisingly my computer booted up with my original MB) the CPU is not sending enough power to the RAM sticks???
I have no idea how the CPU and motherboards work in depth, maybe someone could figure this out and I could do some overclocking settings for the RAM to give it more power to be able to give me a full 8GB.
I should probably tho get this CPU pin fixed.