FSX Full verison, install, uninstall disc errors

[Sgttai]

Well first of all hello and let me say how this started, Im flying in a Cessna skyhawk and all of the sudden Your trail has expired and blah blah blah, which I dont know how this happened, because I entered the product key in a year ago, so what I did was try to find where i could enter it agian, I couldnt find it so I uninstalled the game, then try to install, I got to the end and i got this error :This patch package could not be opened. Verify that the patch package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer patch package.

D:\Microsoft Flight Simulator X.msi
BTW i have it on desktop too and when i click on it i get I have the game on desktop but when i try to play i get: The ‘Dem4km.bgl’file is missing or damaged. Please reinstall Flight Simulator to restore or repair the file. Flight sim will now exit.
So I go to add remove programs and what do ya know it still is there, so I try to remove it and I got this i think: C:\WINDOWS\Installer\81cce.msi
Then i try removoing from disc and i get erros, I have the Full verison of FSX Deluxe, I had for a year and this happend, I tried system restore, i try deleting regerstry keys or what ever they called, any help would be appricated