Instructions:
1. Download
2. Edit file, change "EXE Path" to the appropriate path (eg: C:\\Program Files\\Microsoft Games\\Halo Combat Evolved)
3. Double click / open, allow registry entries to be added.
That's it, then you will be able to update to Halo 1.09.
For Halo Custom Edition, change "[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Games\Halo]" to "[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Games\Halo Custom Edition]" or "[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Games\Halo CE]" and the "EXE Path"