Visit This Gog.com page:
http://www.gog.com/game/raiden_legacy
This is the Raiden Legacy package-- so it includes Raiden, Raiden Fighters, Raiden Fighters 2, and Raiden Fighters Jet.
Unless Raiden was released as freeware-- (Whoop! Whoop! Not posssible!) Then it's time to take Raiden off the site...
We see our 16 year old (Or however old it is) game grow up slowly... It's time to go to college, game. GOG COLLEGE. This is where you'll become a GOOD OLD GAME. Oh, and don't forget to pack underwear and get your school vacinations. And no matter how good the COAST GUARD MAY SOUND, DON'T DO IT.
CYA!