Help! I think I may have caused analog input to disappear. It's a G5 2ghz PowerPc. I only have digital input available in the SOUND PREFERENCES. It should also offer ANALOG INPUT, shouldn't it?

I may have screwed up this Mac somehow. I have been setting it up after a migration from my old G4. I've replaced some pLists and I wonder if that caused this to happen. I had Audio input working previously on this G5, but now it's gone.

Do I have to do an entire OS re-install?

Someone advise me please. I really need this mac audio for so many things, not the least of which is to talk to my son in China via Skype. It's the only way I can reach him.