High Commit Charge but Low Used Phyical Memory

[futahorse]

Gentlemen,

I recently installed two 4GB sticks of DDR3 into my desktop after one 2GB stick failed(I took out the 2gb pair). I've noticed that when multitasking or playing video games, or both, that my commit charge is near 100% but my used physical memory is still at 50% or lower. If I keep increasing the memory usage in my applications or run more, Windows will eventually warn me that I am out of virtual memory though I still plenty of free and standby memory left. My pagefile is set to 2056 max but it is never utilized in any significant manner. Any Idea as to why Windows wont utilize more of the RAM instead of just "running out"?

Specs:

Phenom II X4 965 (3.4GHz)

Radeon 5850 2GB

RAM: 8GB

64bit Win 7

Mobo: MSI 890FXA-GD70

I'd appreciate your input.