Hey there

So my father uninstalled Acceleration somehow during my exams and today when my exams finished  I decided to do fly in VATSIM and when I open up FSX, I got a Fatal Error Message on start up. Happens to me a lot. I could fix it by uninstalling Acceleration and Re-Installing it. But now I cannot install acceleration again as when I open setup.exe it just does nothing.... The loading icon appears on the cursor but goes away. Nothing. No error messages. When I checked the task manager, I saw that setup.exe appeared and immidiately disappeared in the task processes section. When I try to uninstall it from control panel to clear any left over registries so that I can re install it clean, this message pops up.

Any idea? 

Sounds like you accidentally uninstalled FSX with all of your uninstalling/reinstalling Acceleration.  If the installer does not see FSX installed in the System Registry (not in any directories), it will not install Acceleration.  I recently get a similar warning.  I have Windows 10 and did a Windows reset.  Well, reset did not uninstall FSX OR Acceleration OR any of my Addons as they were all still there in their directories.  The Removed Apps list that Windows provided after completion of the reset stated I needed only to reinstall Acceleration.  Got the error msg as you got.  Reset program had evidently removed all of my addons, FSX, Acceleration, P3D, and all of those addons, well, everything.  I had to reinstall everything.

To see if FSX is installed (even though you see it in a directory), just insert the FSX disk and, if it starts installing without giving you an option to remove or do a repair, then it is not installed.   It took me only 5 hours to reinstall FSX (just FSX) as I got the infamous 1603/1722 error msgs.  Finally got it installed and activated and then installed Acceleration with no problems and got it activated too.  The next few days I finally got all of the addons installed.  I intend to write a book about all of my exploits some day soon. 

Best regards,

Jim