I have the Airbus X by Aerosoft and I need to run FSX on compatibility Mode(Windows XP service Pack 2) for the plane to work properly
That's really shouldn't be needed, XP Compatibility mode has lots of other side effects, like problems with disappearing objects and even performance problems.
The Aerosoft Airbus works without setting the XP Compatibility mode without any problems: the reasons why they advice to run in XP Compatibility mode, it's likely because the product tries to write into FSX folder (or the FSX\Gauges folder or any other folder inside FSX), and this is by default forbidden under Vista/Windows 7, since proper Vista/Windows7 apps should only write into the %APPDATA% folder, like all our products correctly do, for example.
The issue is, FSX is by default installed into C:\Program Files, which is why some developers requires either you run FSX As Administrator (which might be one solution) or using the XP Compatibility mode, which is probably the worse possible solution, because of all the other side-effects and compatibility problems with other proper Vista/Windows 7 apps that are run at the same time.
A much better solution would be changing permissions for your FSX folder (and subfolders too), and give your user account write permissions to it, you can do this by right clicking on the FSX root folder, select the "Security" tab, click on the "Edit.." button, then "Add" your user account with "Full Control" permissions.
Or, look here for a more detailed explanation:
http://www.mydigitallife.info/how-to-take-ownership-and-grant-permissions-in-windows-vista/This is the same as installing FSX into a custom folder, which is usually a smart thing to do, to deal with non Vista-compliant addons that needs to write in the FSX folder, but in this case you don't have to reinstall FSX.
