1. Right-click Start, and then click Explore.
2. Click the hard disk where Flight Simulator X is installed. (Your "C" Drive)
3. Double-click the Program Files folder, and then double-click the Microsoft Games folder.
4. Click the Flight Simulator X folder.
5. Highlight it, click Delete.
6. Click Yes to confirm that you want to remove the folder and its contents.
To make it easier:
Open any folder and delete as much as you can at one time then go back for more...it'll take more time that way but it's easier for you to do.
Go to the recycle bin occasionally and empty it. It can't holds 15 gigabits.
1. Click Start, and then click My Documents.
Right-click the Flight Simulator Files folder, if it exists, and then click Delete.
1. Click Start, and then click Search.
2. Click All files and folders.
3. In the All or part of the file name box, type FSX.
Delete all that has to do with FSX
Remove registry entries for Flight Simulator X
Use this regvac. Use the demo version to clean the registry.
Important use the novice button to do this if you don't you may crash windows.
Click start/programs/Microsoft Games and delete FSX, if it's still there.
Now you can reinstall, launch it without adding anything.