DesMuMe emulator is the best DS emulator out there, hands down. It's build quality and efficiency is almost as good as a real DS. You can access all available features of a real DS ,on the emulator as well. Except for Wi-Fi emulation doesn't exist. (Some svn builds have wifi) Using emulators and roms is considered illegal and I strongly advice to go legally if possible. For more info on emulator : www.desmume.org