sorry for copy&paste from Strike Fighters Knowledge Base:
"In Strike Fighters Project 1 and the other “1st Gen” games in the TW series (Wings Over Vietnam, Wings Over Europe, Wings Over Israel), any mods or addons were dropped into their respective folders in the game’s main install directory. That is no longer the case with the “2nd Gen” games (Strike Fighters 2, SF2V, SF2E, and SF2I).
Any mods or addons you download for the 2nd Gen games will most likely include a reference to a “mod” folder somewhere in the readme, where the user is supposed to put the downloaded files. However, there is no folder (nor should one be created) called “Mods”. The following is to help you understand what the “mod folder” is really referring to.
When a 2nd Gen game is first installed, the game needs to be run at least once so that the game can create the “mod folder”. After the first time you run the game, a set of directories will be created in one of two locations, depending on whether you’re running XP or Vista/Win7. Assuming you ran the .exe for Strike Fighters 2, the directories created are as follows:
C:\Documents and Settings\<username>\My Documents\ThirdWire\StrikeFighters2 Israel\
C:\Users\<username>\Saved Games\ThirdWire\StrikeFighters2 Israel\"