Please perform a "factory default" reset on your AirPort Express. Note you may need to do this a few times to make sure it "sticks." Once completed successfully, the status light should flash amber NOT green.
This type of reset will reconfigure the Express to its factory settings. That is, it will broadcast an unsecured Wi-Fi network with a network name (aka SSID) of something like: Apple Network NNNNNN
Can your Win7 computer find and connect to this network now? If it can, then do so and the AirPort Utility on the PC should now be able to find the Express.