I have a new computer that is running vista. I transfered my 747-400 PMDG from my old computer which had XP. Everything works fine except the auto pilot will not engage. It worked fine on XP. Any suggestions ? thanks.

Did you transfer or reinstall? The program needs to be installed not just moved.

Thanks for the reply, I reinstalled through PMDG. a little more information, when I engage the auto pilot L C or R, it displays that it is engaged by the CMD symbol on the ADI.But it Will not engage in any modes on the MCP, Vnav, Lnav,FLCH, or Vspd. Doug Morlan

First off, you can rule out Vista where the only problems seem to be with rights to change files but I don't use Vista so this is the extent of my knowledge.The autopilot will not engage for any number of reasons, including incomplete preflight, flight plan problems and so on. Does autothrottle work?