Location of the fs9.cfg:
Windows XP : C:\Documents and Settings\[Your Username]\Application Data\Microsoft\FS9
Windows Vista : C:\Users\[Your Username]\AppData\Roaming\Microsoft\FS9
Note: "Hidden files and folders" have to be disabled in order to see this file.
To do so:
Control Panel -> Folder Options -> View Tab -> Scroll down and put a bullet in "Show hidden files and folders" -> Click "Apply"
I installed the original aircraft, 'Mig19_v1.zip', and everything is ok. I would suggest installing just the original. If everything is ok, install the new texture add-ons 1 at a time, checking each one out as you go.
Added: If you're getting the error on the splash screen then you probably have saved the default flight using one of the mig repaints. If you haven't already deleted the FS9.cfg file, you can open the fs9.cfg file and look for this entry:
[USERINTERFACE]
MAP_ORIENTATION=0
PAUSE_ON_LOST_FOCUS=0
PROMPT_ON_EXIT=1
PageID=3
OpenATCOnCreate=0
SelectFlightLevel=0
SelectFlightTitle=0
DisplayFuelAsWeight=1
SITUATION=C:\Documents and Settings\dave\My Documents\Flight Simulator Files\3cu
At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation.