I have been using FSX as most of us have and wanted to go back to FS9 to fly a few United Virtual flights for the airline and went to change the load for the 737 flight and got the error that said Could not detect a valid flight simulator installation. I thought that was strange as I didn't change anything ith FS9 so I fired up the sim and was going to take a look to see what I got. The plane loaded okay and I was reading it for take off and a little test flight jsut to make sure. Once I started moving my frames that usually are around 30-40 everywhere in FS9 with all the addons, dropped to 1-2-3-6 once I changed views and went back into the cockpit. I have hunfredes of hours in the 737 and never any problems but one thing I noticed was that if I hit the ALT key in every view but the cockpit the frames would come back to normal. Any thoughts or suggestions would be great as I lovet his aircraft. I have a new Intel Core 2 Duo 6600 and 2 gig of ram along with the Nvidia Egeforce 7900gt ko and I have not had a single problem with it in the past even with the 737 and I have flown it lots because I can go anywhere with any scenery and all the AI aircraft and never have any frame rate isuues. Again, any info would be great. I havenot yet trried to reinstall as I didn't wantto loose all my addon liveries.Thanks Shayne

Did you install FSX? If so see messages pinned at the top of the forum.