Root: HKLM; SubKey: SOFTWARE\Wow6432Node\Bethesda Softworks\
Fallout 3 - DLC DE; Flags: uninsdeletekeyifempty
Root: HKLM; SubKey: SOFTWARE\Wow6432Node\Bethesda Softworks\
Fallout 3 - DLC DE\1.00.0000; Flags: uninsdeletekeyifempty
that will only work if the DLC you installed was german, if it was the English version it must say EN. But regardless, the DLC.rar I posted does make the DLC show up, when running from FalloutLauncher.exe
Don't know why it doesn't run from having same entries in the [Registry] section of the ISS script.