Go into services and check Bluetooth is set to start automatically as opposed to manually; I had non-pairing problems with an HP Bluetooth mouse on a Kensington dongle which was solved by doing this
At first I had imagined there was a compatability issue and thought I'd have to get another mouse, but the solution was the BT service just wasn't running by default, although in my case that could have been due to the dongle not being there when Windows7 setup was originally run...