I've done many Reinstalls due to hardware upgrades.Though i went to reinstall it and when it finished but it didn't ask for an activation code, I went to test it and it worked fine.When i tried to install SP1, It gave me an error saying it couldn't access a key. so i uninstalled the game through control panel and reinstalled. Same problem.How do i Fully uninstall this game?

Are there registry entries that need to be deleted?

How would i be able to check?I've done a registry cleanup using CCleaner

1). Unistall Acceleration OR SP2.2). Uninstall SP1.3). Uninstall FSX.4). Completely delete the "Flight Simulator X" directory from the drive.5). Check your personal folders/files for the Shader files, your .FLT files, your Logbook.bin, your AppData, Local and Roaming files: if they still exist - copy them somewhere else and delete those on disk.6). Do a Registry clean and purge all remnants of FSX. Reboot. It will now be ready for a fresh installation.Anyone - if I've missed something - chime in.

If you are getting Error 1722 try this first. This should fix it.http://support.microsoft.com/kb/928080

Had this exact error. Actually went through MS PSS to get help. Turns out I hadn't uninstalled it properly. It is possible to uninstall FSX and NOT uninstall SP1/Acceleration!! Crappy uninstall routine if you ask me. I tried everything (and I am a computer engineer!) and nothing worked. It is actually finding a folder in the installshield registry. I can't find it now on mine, but try running the Install Shield error fixer from microsoft. Also, make sure the %systemroot%\ProgramData/Microsoft/FSX folder has been deleted.MS should really put a check in the uninstall for FSX that checks to see if SP2 has been uininstalled. Also, when you have correctly uninstalled SP2 and rebooted (VERY important) you will have the vanilla non-SP FSX uninstall still there. Run it again to remove original FSX files. If this isn't your issue, I apologies for hijacking your thread!

You could also reinstall Windows. I know it is a major hassle and inconvenience, but it declutters my system and makes everything run faster. I usually do that about every 18 months.

Alright, i've gotten everything off, That is FSX, The service packs and Acceleration. As well as the addons associated with it, I used an uninstalling program called Revo.I managed to delete many registry entries as well, Let's see how this install goes...