Hi, I have an i7 860 but with a GB P55A-UD4P and 4GB of Gskill eco Ram and I have the same problem. Press the windows button and where it says search programs and files, type in dxdiag then go into it. Under system it says- Memory:4096mb ram (windows recognizes all 4GB) but when I go to display, it say-Approx. Total Memory: 1784 mb for my graphics card which is a ATI 4890 oc . Now the problem is that on the box it says my card is only 1GB so where the extra 784mb comes from I don't know, maybe windows is getting the extra ram from my GPU is actually borrowed memory for my 4gb ram. And if this this the case then this would explain why when I go into systems under control panel it says 4.00 GB (2.00 GB usable) because it is borrowing memory from my ram to use in other applications/hardware. I tried everything to try to change it but I can't seem to find the solution. Windows experience index also gives me a rating of 5.5 for ram, maybe because I'm only really using 2GB, if we could find a way to change this than I guess the rating would go up. Anyways besides that, my system runs smoothly. I've ripped DVD's, some downloading and watched another movie at the same time and my sytem doesn't even stress so I'm not that worried about that extra 2gb, so unless you need it for doing even more than that and your system starts slowing down , then I wouldn't stress. Hope this helps.
It don't think its a defective stick, because I've tried swapping mine around also and the same thing happens. So I think it either the windows i am running(windows 7 x64) or Gigabyte have made an error with their bios settings. I've updated my bois from the GB site and rebooted but still nothing. If you have fixed the problem or found another solution, please let me know because it really starting to anoy me alot. Thanks