Problem with memory in Win 7 64 bit

In normal bootup mode in Control Panel/System it states that I have 6gigs of ram and only 2.75 usable. If I go to misconfig under boot/advanced options and type in mt total ram I have installed then click ok and apply and ok again and reboot,then under Control/System it shows that I have 6gigs of ram and now 4.75 usuable which it should be.I am running Windows 7 64 bit why do I have to do this?. My question is why doesn't it do it under normal boot.I checked out each stick of ram and they are fine,I tried to find memory remapping in my bios ,but to no avail.It's a XFX680iLT.:confused Any help would be appreciated

__________________

 

Are you sure your running 64 bit?

 

Yes. I found this . Seems to work.http://www.sevenforums.com/tutorials/66482-memory-set-maximum-amount-used-windows-7-a.html