Finding the right Bluetooth adapter

I'm not sure if this is the best forum to post my question in, but here goes. I am looking for a Bluetooth adapter for my Windows PC that has built in serial port emulation. By this I mean that after I plug it in, it will appear to Windows as COMx. Apparently this is not always the case and the first adapter I bought does not have this feature. Since I want to control part of my Arduino project from a C# program running on a PC, I need the Bluetooth module to appear simply as a serial port without me having to find and install third party drivers. If you are using a BT dongle and can give me a make and model, I'd appreciate it. Distance between PC and Arduino project is not an issue. They will be in the same room.