Jtagging allows you to fake licenses from the marketplace, effectively letting you play live arcade games from the hdd or a flash drive without having officially downloaded them. I modded mine to play burned 360 games, because I already have a computer for emulation, and PS1 emu on anything but a PC or a PSP is shitty. The only real reason to mod a 360 is to play burned games. If you're looking for perfect PS1 emulation, pick up a PSP. Its the easiest thing to mod, and it runs every PS1 game perfectly. If you really need a console for classic game emulation, I would say to look for a Dreamcast, or softmod a Wii. Or just use a PC, since it doesn't get easier than that.