Just copy the game to your memory sticks ISO folder and run custom firmware.
[color=red]Here is the link needed to mod your PSP http://www.psp-hacks.com/forums/f118/idiots-guide-to-building-a-magic-memory-stick-t214330/post1039148.html[/color]
Shoot, attack, and stave off the assault by defeating all the Invaders on the screen. After annihilating a battalion of Invaders and defeating the Boss, players move on to the next stage. But beware of different types of Invaders, each with their own unique abilities – it's "Game Over" if players lose all of their stock cannons![/color]