Nowadays not all computers have a serial port, and hence if you have a serial device you need to purchase a USB-to-Serial adapter. As I mentioned in my previous post, the Parallax RFID Reader Module uses a serial connection and hence you are out of luck if you do not have a serial port (or do not want to spend the extra money to buy an adapter). Fortunately, you have other choices - the Phidget RFID Reader is one of them. It is a read-only RFID reader that supports USB connections. Instead of reading the tag IDs through the serial port, it comes with an SDK that supports .NET. You just need to use the SDK in your .NET application and service the necessary events to retrieve the scanned tag ID. It comes with a slightly higher price tag, though, a complete kit (contains tags of various sizes) costs $79.25. Check out the kit here.
Special thanks to Matt Trossen and Jennie Jetter from Phidget for assisting me with the RFID reader!