. Install CFS 3 normally.
2. Install the 3.1 Update (CFS3UpdateEng.exe).
3. Install the 3.1a Update (ACUpdate.exe)
I highly recommend complete un-install and a complete re-install.
1. Uninstall CFS3 normally.
2. Delete the Combat Clight Simulator 3.0 folder from its location in C:\Documents and Settings\User Name (Your Name)\Application Data\Microsoft.
3. Delete the Combat Flight Simulator 3.0 folder from its location in C:\Documents and Settings\User Name (Your Name)\My Documents.
Note: Despite having the exact same name, these two folders contain entirely different files, and both folders need to be deleted before re-installing CFS3.
If you can't find the Application Data folder in the User Nam (Your Name) folder, you need to do the following:
To find XP Application Data folder, open your Windows XP browser and look for the Tools tab at the top. Click on it and look for Folder Options. Click the View tab and look for “Hidden files and folders”. Make sure “Show hidden files and folders” is checked. While you’re here, also make sure that “Hide extensions for known file types” is unchecked.
Thanks Grizzy --this is copied and pasted from one of his threads grizz rocks "