I'm embarassed, but I really cant solve this...
The computer is running XP, not sure whether it's SP3 or SP2 though. I'll check that next thursday if it matters. I'm trying to get a Microsoft bluetooth mouse up and running.
So, I did find the software for it, it told me to plug in the receiver and let the automated driver install do it. Fine, not a problem. Then it told me to open "Bluetooth Devices" from the control panel. But this was not to be found there. I located the bthprops.cpl file, and tried to run it. Nothing happened. I checked the version of the file but forgot to write it down, it was 5.something...
I've seen that this is what happens if there is no supported bluetooth receiver installed, but the device manager tells me it has installed properly. Haven't been able to check that but I can't believe it's not supported, since it's a Microsoft device!
I additionally tried connecting the very same receiver and mouse to my Win7 laptop, it worked almost instantly. Then I tried replacing those registry keys with those that worked (they were rather similar), but to no good.