Hello...I dont think it would use RAM but i dont know for sure...but yah it can easily be disabled. All you'd have to do is right click on My Computer,go to properties, go to Hardware and go to device manager. Then, right click on the onboard graphics card and go to disable. Done!
Also, thats not a pci express card..its an AGP card. You might wanna make sure your computer has AGP. But besides that its a pretty good card.
Computer Systems Tech