Steam News announces the release of METAL SLUG on Steam, offering the chance to play the original game in this run-and-gun action game. Here's word on the PC version of the game, though they note this will not run under Windows XP:

MAIN FEATURES

• ARCADE MODE (MAIN MISSION):
  Play the original arcade version of “METAL SLUG ” with its charismatic protagonist soldiers Marco & Tarma, maneuver the almighty “METAL SLUG ” tank, and fight your way through the 6 missions of the game to thwart Gen. Morden's evil ambitions!
• MISSION MODE (STAGE SELECT):
  Play and enjoy your favorite stages at will! Train alone or with a brother-in-arms on the missions you have unlocked so far!
• ONLINE MISSION (ONLINE MULTIPLAYER):
  Connect to Steam and clear missions with a brother-in-arms far away via the Online Co-Op Play feature.
  Engage with a fellow countryman or foreign ally and let the mission begin!
• SETTINGS:
  Configure control, language, video display, and sound volume settings for the best “METAL SLUG ” experience on PC.
• LEADERBOARDS:
  Check your current rank & score in “METAL SLUG” at any time, and challenge other players to be the best “METAL SLUG ” soldier in the world!