From here. Works on these knock-off mini-dongles from DealExtreme. If you have this exact dongle, you can skip all this and just use my hacked INF.
USB\Vid_1131&Pid_1004". Press Ctrl-C to copy this entry to clipboard. Save it for later.%windir%\inf\bth.inf" to another directory.[Cambridge.NT.5.1]" section.My wacky dongle=BthUsb, USB\Vid_1131&Pid_1004", except replace the bolded part with the string you copied earlier. You can change the name to whatever you like. Save the file.bth.inf" file we just edited.