There is PACK, by actorbug. It's a program that compresses multiple files into one. Just copy PACK, UNPACK, and your files into a new folder, run PACK, select which files get compressed, save the DAT file, and delete PACK. Then to decompress it, just run UNPACK. The program is in Japanese, but it's easy to use. Just make sure to keep a backup just in case.
Key: 74N3F3D4
2そうだね プレイ済み