The amount of memory available is accurate, but it includes what the operating system is going to give the video card from system RAM. The amount used is only accurate in Windows XP. Microsoft broke the function which reported the amount of used memory in Vista, and all versions of Windows after that.
We will probably remove that line in a future release.
I need a DXDIAG output to better answer the performance question. Also note, it is quite possible to configure the game to cause performance problems with your video card.
One last thing. If your computer only has 2GB of system RAM, and you are running any operating system other than Windows XP, your computer is not going to have enough free RAM to run the game without running out of resources, especially if you configure the game with any of the graphic details enabled.