Make sure you do this with the dongle out of the PC.
1. Go to "Device Manager", find your bluetooth dongle, double click on it to open properties.
2. Go to the details tab and select "Hardware Ids" from the drop-down-menu. Make a note of all the values, usually there are 2.
3. Do a search on your Windows drive for "bth.ini" (on vista it is in the "C:\Windows\inf" folder IIRC).
4. Make a backup.
5. Open the file in a text editor and scroll down to you start seeing lines like: "Motion Computing USB Bluetooth Device= BthUsb, USB\Vid_10ab&Pid_1002".
6. Edit one of the lines changing the end bit to your hardware id.
7. Save the file.
8. Stick the bluetooth dongle in, if it fails to install go back to step 6 any of the other hardware id's you got in step 2.
9. Copy your new bth.ini file incase you do a reinstall.