Well we cant tell you what it would be capable of graphic wise. We have no idea what machine you have or its internals. So for us to tell you would be like trying to play psychic for the world. Check your System Information by just typing in System into the Start Menu to see what it says under Compoments>Display and that will tell you much more information than anyone here can.
Windows 7 is just the Operating System. It isnt a gaming platform, it isnt made for gaming. It is made to operate the PC. The games are developed to operate within the OS, not the other way around like a console. I dont know why you would think that it would be anything like a console, when it is a PC. Games are no different than any other piece of software for a PC. It doesnt matter if it is Windows 95 or Windows 2095. The software will be designed for the OS, not the other way around. There is no comparison from PC to Console. They are 2 completely different platforms just like Windows is to OS X is to Linux.