ROMs are a digital image of an existing game. Many ROMs on the Internet are illegal – make sure you only download public domain or free license ROMs. Roms are great though and with the controller for the pc it makes it even better. I know they have out now like ps2 emulators and what not but i found it to be a waste of time.

Emulation violates copyright law pretty much every time a user runs an emulator–unless you’re copying the ROM from a cartridge you own yourself directly to a computer. Even if you own a copy of a game and system, if you download that game for an emulator you’re making an unauthorized copy of a copy you do not own, so it doesn’t strictly fall under fair use rules.