The game installation consists of two things.
In Windows 7 or Vista you have to either use the modified installer disk, or manually install the game.
[HKEY_LOCAL_MACHINE\SOFTWARE\LucasArts Entertainment Company\X-Wing vs. TIE Fighter\1.0] ... "Executable"="c:\\games\\XVT\\Z_xvt__.exe" "Install Path"="c:\\games\\XVT"
Note: Enter the pathes exactly like this. Mind that backslashes have to be entered twice in a row. This is called “escaping” and is necessary. Note: The value “Source Path” is the name of the CD-ROM where it is installed from. However, this value is ignored by the game, so it's not important.
Download xwa.reg and use this file as described in the previous chapter.