The mouse mouth has to be powered on first, and the bluetooth receiver has to be plugged in also, before you power up the PC. If it's still not recognized, you may have to do the device's simple signal sync procedure, which usually involves pressing a button or two, and watching the blinky lights.
(Also don't chew marshmallows or watch Star Trek while you try to sync, or type. "Beam me up Snotty. I'm blue in the tooth." )
I have win xp home service pack 2, amd anthalon 64 3500+,1 gig ram and ati 9600 series video card. I installed blue tooth drives and was able to get my kignston mouse to work after adding it to devices. The problem i am having is that when I re-boot the pc the mouth is not recognized on star up and I have to plug my wired mouse back. Any help will be greatly appreciated.