I have a gamecube that shows "disc error" whenever I try to play it. I know the discs work because they work on my other gamecube. Also, if I leave the gamecube on for 1/2 an hour, then try several time to get it to work, it starts working sometimes. If it does start, it plays well until I shut it off. Any suggestions?
Try cleaning the lens and see if it helps at all. Either get one of those store bought kits or be cheap (like me) and use a Q-tip and rubbing alcohol to carefully clean off the lens. Also, clean up the games if they're dirty as well using a kit or a cotton ball and rubbing alcohol. If both of those things don't help, chances are the lens and/or motor are crapping out.
Or that. I usually only reserve that advice for back-ups though, since retail games should work just fine on any Gamecube. The only time retail games shouldn't work is if the lens is dirty/damaged or the games are dirty/scratched.