Now that I think about it, I do have to press Play. Not sure if there's any way around that in PowerDVD.1. If a BluRay disc is already in the drive, and MediaPortal is running, when I hit Play BluRay it opens PowerDVD and hides MP fine. The problem is that I have to hit play for it to start playing, otherwise it will stay on the blue skin screen. It's minor but autoplay is nice.
Sounds like your Windows Autoplay is kicking in. In Vista: go to Control Panel -> Autoplay. I disabled all of my Autoplay options. Now when you enter a Bluray nothing will happen until you press "Watch Bluray" in MP.2. If there is no disc in the drive, and MediaPortal is running, and I put a BluRay disc in, it launches PowerDVD, but does NOT seem to launch the version of it that I want. This version does not have a blue skin (it's black), and does not respond to any of my keyboard commands. When I play a disc the correct way in #1 above, PowerDVD responds to my keyboard commands and if I hit escape will go back to MP. So my question is, how do I disable the autoplay of this "rogue" version of PowerDVD, and get it to autoplay the HD_Starter exe as if I were to hit the Play BluRay menu item?