For no apparent reason the cd tray on my Mac G4 (about 3 years old) suddendly came out as if to eject a cd. I have tried pushing it back in, but it immediately comes out again, no matter whether there is a cd in it or not. When there is a cd in the tray, the computer does not read it before it ejects.

Is there anything I can do to remedy this or do I have to get a new CD drive? If so, internal or external? Any suggestions would be very appreciated.

At least try jiggling the eject button. Also restart if you haven't. Maybe try reinstalling the CD extension. If you have much electrical/mechanical experience, take it apart and see if the eject mechanism is stuck somehow.

Internal is good. I recommend a pioneer... I bought one for $43 installed myself.

Pioneer DVR-112D [Beige Bezel] 'SuperDrive' 1... (DVR-112D) at OWC