I think those "experts" at that Microsoft site used that reply as a standard catch-all response to *any* user reporting a problem with *any* program when used under Windows 7
There are many flaws in that reply:
- The MS moderator suggested that the XP compatibility mode should be enabled, on the reasoning that the published requirements for FSX were "XP / Vista", but they were published as such, because in 2006 when FSX was released, Windows 7 wasn't out yet AND when a program requirements says "XP / Vista", it means it will run in EITHER, not that it "requires" something from XP.
- As a general rule, something that runs in Vista, does't have the slightest issue under Windows 7 and doesn't require the XP compatibility mode. You need to turn on "XP Compatibility" mode ONLY when something runs ONLY under XP.
And besides, the question posed on that forum was the user asked why he couldn't quit from FSX under Windows 7. Since this doesn't happen, it's likely the user had some 3rd party addon that wasn't compatible with Windows 7 and created issue which, incidentally, might have fixed this problem for that user, without this meaning that FSX would run best with it.
In fact, the XP Compatibility mode does many tricks to make the software believe is running under XP, like changing the OS version number reported, redirecting the read/write to system folders, redirecting the registry, and this create problems with products (like our own) which ARE FULLY compatible with Windows 7, since our installers correctly check the OS version number to install the proper files in the proper folders, using the proper registry keys depending on the OS and respecting all the possible permissions issues related to Windows 7.
So, if the installer, which of course detects a real Windows 7 running, installs everything correctly for Windows 7, but FSX is set into XP Compatibility, once the software runs everything goes wrong, because the software is forced to believe it's running under XP.
That's why XP Compatibility should be off, because it's dangerous for products that ARE compatible with Windows 7, and all our products are, and FSX itself is.
Note that, most of the problems some 3rd party addons might have in FSX under Windows 7 ( not our own ) might be solved more safely by simply running FSX As Administrator, or changing the FSX folder permissions to read/write for all normal users.