You can just copy the Langscript.iss from previous version. Then see post #30, for the correct entry & how it should be entered in the [REGISTRY] section of the script.
NOTE:
clriboli just changing the path to {app} from a FULL location DOES NOT WORK.
Code:
Root: HKLM; SubKey: SOFTWARE\Bethesda Softworks\Fallout3; ValueType: string; ValueName: Installed Path; ValueData: {app}; Flags: uninsdeletevalue uninsdeletekeyifempty
However having the
full path DOES WORK, but limits to where you can install game to.
Code:
Root: HKLM; SubKey: SOFTWARE\Bethesda Softworks\Fallout3; ValueType: string; ValueName: Installed Path; ValueData: C:\Program Files (x86)\Bethesda Softworks\Fallout 3\; Flags: uninsdeletevalue uninsdeletekeyifempty