Are you using Windows 7? And you are not using an integrated graphic card? If so, 2 GB is being shared to your integrated graphic card.
It is win 7, and it's not intergrated, I have a GTX 550 TI, but honestly there's somthing funky going on.. I just tested to make sure I didn't have a bad stick, it will boot with BOTH but not ONE. I got it to boot with one the first time I tried, but every attempt since has resulted in a blank screen with no post
(no keyboard flash that I saw), but it's a long press turn off.