You need a DMS chip to get a ATAD patch for your regular HD and then install through the game's INSTALL feature. This leads to slowly installing the game (it will take about 40 minutes. Thats how long it took for Metal Saga, but it loads at game speed so you don't mess up your Laster at all). Then it works like a HDL Cd, you just put in the game, it starts up the game, BUT doesn't read off the DVD instead reads from HD. You just need the game IN the tray (never know when it will checkto authenticate). This is a solution to this game. I hope this helps those are looking for a way to play off HD. All credit to Davion for making me aware of this method for Metal Saga and now this (and perhaps Dirges of Ceribus).
1. You need to go to DMS Chip set-up screen. For DMS4 that uses toxis BIOS or OS, you will need to press square button when you start up your PS2 Enable ATAD-auto-patch mode, reset your PS2
2. Start up Metal Saga game, normally there will be only 2 options "New game" and "Load Game", if you did step 1 correctly, you will see "HD Install" as third option
3. "HD Install", and just wait until finish
4. From this point on, when you play, the game will load everything from HD, the disc is still required when you enter title screen (exit game, start game, etc)