Looking for a ROM Player for NES or Genesis/Mega Drive

[Epicenter]

Hey, I'm looking for a device that'll let me play ROM files (from floppy disks) on my NES, or Mega Drive / Genesis. I know the Super Magic Drive and (Game Doctor?) do this for the MD, but I haven't been able to find one. :( Does anyone have one, or could you point me in the right direction?

Thanks. :)