Hello Everyone: Not sure where to begin here. I had everything working absolutely great on my system (vista + fs9 + fsx demo). Then I decided to uninstall the fsx demo as I was hardly playing it. Now, after uninstalling the fsx demo, it takes a very long time (3+ minutes) and my computer's load jumps to 100% whenever I select any PMDG plane -- the wait is when reading the AIRAC cycle. Previously it was barely a hiccup to read the cycle. Once the plane is available, the entire panel is VERY slow, very choppy. Trying to enter a flightplan in the FMC takes a very long time; not really sure why. Huge lag in the system. Once the plan is entered, the entire simulation's framerate crawls to unplayable status. Please note -- I had NO problems running the system with its current settings before uninstalling FSX and updating the AIRAC; and my system (Core2Duo 2.6 Ghz with 4 GB RAM) is clearly above the minimum specs required for the game. I was previously running the simulation with PMDG aircraft on full/high resolution (all sliders maxed) without any problems. Finally -- this issue is only with PMDG, as with the PSS 777 I have no such framerate/lag issues. I would appreciate any tips.

Uninstalling the FSX messed with the FS9 registry. The normal symptoms are FS9 not found by an installer.. see the pinned topic above. There is a download utility available to fix this.

I don't think this is the problem in my case, since installers are able to find my FS9 directory correctly (I have installed an AIRAC update since then).I will try to uninstall PMDG and re-install it again in hopes that it helps.