Motherboard not using / even locating all physical RAM installed?!

Hi. Im not very experienced with overclocking / fiddling with hardware, so I'm looking for some help! Today I got my hydro 100 CPU cooler in today and wanted to pump up my i7-920 up a bit..
Everything seemed to work like a charm until I realised something.
My computer is only using 2 GB ram out of my 6 GB installed ram. First I thought it was a OS problem (Using windows 7 ultimate), but realised its not.
Both in windows and in my BIOS it looks like there's only 2 GB physical RAM installed, even though I have all 6 slots loaded and they're all somewhat equally warm when I've been running the computer for hours!

The two highlightet ones says (the OS is in danish):
installed physical memory: 2,00 GB
physical memory in total: 1,99 GB
http://img46.imageshack.us/img46/1051/msinfo64.png

I overclocked my i7-920 to 4gz and didn't really tweak or do anything to my RAM settings other than following the common voltage recommendations. I even tried to reset all of my BIOS settings and remove my overclocking tweaks in order to see if it'd help. But it didnt.
http://img269.imageshack.us/img269/4...ardcpuinfo.png

Here are my voltage settings as well:

RAM info picture below - All the ram slots from 1 to 5 are identical. The 6th RAM slot is blank?? Dont know why.
http://img225.imageshack.us/img225/6894/memoryinfo.png

Took a picture of my motherboard setup with all the ram plugged in. Link here:
http://img97.imageshack.us/img97/1360/thesetup.jpg
And a closeup picture of a single block of RAM. All the ram im using is the same type bythe way:
http://img708.imageshack.us/img708/8194/ramcloseup.jpg

Would be super awesome if anyone can help! I tried to recompile my computer from scratch but no luck again :(