I did a similar hack to ZZT32's Yaz0->LZO/RC4 hack, except not quite. Unlike his hack, I did not change the format files are stored (he added a 8-byte header to each file, from what I can tell). My code is more naturally in the game - it's part of the 'boot' file. It still supports Yaz0, but it also supports LZO. Implementing this hack on other game versions would be rather simple, and for games like MM, it would make hacking them loads easier.