Windows 7 can only do very limited operations with rs232 out of the box. Also it's absurdly picky about the driver used for rs232-to-usb adapters in my experience so make sure it's popping up under ports in your device manager. In my opinion your better off using third party solutions.
I personally use RealTerm. It's free, open source, and generally works very well. There are, however, a large number of proprietary alternatives.