The other day I bought myself a USB bluetooth dongle for my HP laptop and a HC-05 bluetooth adapter for the Arduino.
When I connected the dongle to my laptop running Windows 8 it appeared like it would install the default drivers for it. I connected the HC-05 to an Arduino and I could locate it from my laptop. I could even pair the dongle with the adapter. (Default code: 1234.)
But when checking the HC-05 in Windows’ device manager its status would say “Offline”. It took me several hours of googling until I came across a suggestion by another user that bought the same dongle on amazon: I installed the Toshiba Bluetooth Stack! Even though it says it’s only for toshiba laptops it worked on my HP like a charm.
I also had a HC-06 adapter lying around. Optically they look very similar. As far as I know HC-05 can work as master or slave whereas HC-06 is slave only. If you use them as slaves you can use either of them using the same pins. HC-05 came up under COM40 and HC-06 identifies itself as “linvor” under COM41.