Memory not recognised, Please help

Hi, i am running windows vista ultimate 64bit and i have a Gigabyte GA-M33S-S3 Motherboard and i recently had this problem:
i recently purchased 2x 2gb sticks of pny 800mhz ram ddr2. i already had in my pc 2x 1gb pny 800mhz ddr2 ram sticks. i plugged in my 2gb sticks of ram in the first two slots and moved my 1gb sticks to the 3rd and 4th slots.
I powered up my pc and it stuck, it didnt load or anything, no response from monitor, mouse or keyboard.
i then decided to try out 1 2gb stick on its own to no avail.
i got some advice from a friend to try out different combinations and this combination finally allowed my pc to start:
slot 1: 2gb stick
slot 2: 1gb stick
slot 3: 1gb stick
slot 4: 2gb stick

I now have a new problem.... when i look at the system properties it says i am running 6.00gb.... but i didnt quite believe it. so i ran dxdiag and found that it said i only had 2gb running.
i found advice from a forum which told me to run msconfig and go to the boot tab, and advanced, and then to click the "maximum memory" box and that would solve it.... but it told me that my maximum memory was 2048mb's.
I have ran Everest Ultimate and it also tells me my physical ram is running at 2048mb's.
It shows all of my sticks installed in the motherboard but where is my memory ??

Can someone please help me ?

CarVeR

I am having same problem, have 8 GB installed (4x2) and it is saying I have 2GB only. Vista properties says I have 8GB but everything else sees only 2GB. I also have Vista Ultimate x64

Enable Memory Remaping in Bios - Chipset section.

mine doesnt see all 6gb in the bios section and i have no memory options in any sections. my bios and mobo suck the earth !
i am just confused as to why my mobo didnt accept a 2gb stick of ram on its own, and this is the only possible combo that works so strange.