What happens when you just plug the USB2SERIAL Light in and Plug the USB into your computer? Do any LEDs come on?
If the PC sees the USB2SERIAL Light, you are going to need this INF file:
http://arduino.cc/en/uploads/Main/Arduino_USBSerial.zip
If it does not Auto-detect, you might need to peek around in your Device Manager to see if it is stalled device.