The only boot disks for PS2 are those that perform a management function first and then allow a game to be hauled in behind it. Examples are:

Action Replay 2/Gameshark 2: for setting up game cheats
DVD Region X: for playing DVD movies of a different region
Memory Manager Plus: for initialising the 16MB memory card
Utility Disk: for JAP PS2s - loading DVD drivers & other admin functions

Without a modchip, the above programs do not allow backups to be played. Only original games for the appropriate region.

With a modchip, the above porgrams allow backup games to be hauled in behind them.