MAME2003 is just one of those versions (based on 0.78). MAME is an emulator with many, many versions.
As a hail mary, I launched from the terminal instead to see if that would work.
SECOND EDIT: I recently made a shortcut to launch Retropie. All the roms I had running now just default back to the Retropie menu after 2-3 seconds. Thanks so much!ĮDIT: NOTHING will launch no on Retropie - not even the menus to configure Retropie itself. If there's anyone familiar with MAME, just 2 mins of your time to write clear instructions would make my entire weekend. Do I also need to download and place the XML files from the source somewhere in the folder structure? However when I to run a rom from Arcade, or Arcade/mame2003, it always just brings me back to the RetroPie interface. I've put the contents of the samples folder from the source into bios/mame2003/samples. I found a source (the most popular one) to download individual non-merged 0.78 ROMs. Hey everyone, I've been working on this for hours and reading so much that my eyes hurt.
