The 5200/6200-series machines and PowerBooks 5300 and 1400 are NuBus, and the 5200/6200 machines are very poorly engineered examples of it. Like others have said, iTunes won't really work on non-PCI boxes (at least it doesn't for me). I use WinAmp Mac (don't know if that's downloadable anymore) or MpegDec (available here: http://www.jwgdesign.com/mpegdec/about.htm). WinAmp works on PPC machines, and MpegDec works on '030s and up, though anything less than a 40MHz full '040 doesn't sound the greatest. It's decent on a 6100, though. If you're looking for an encoder, though, I don't know where one might find something decent. Given the speed of the machine you're trying to run it on anyway, I imagine that encoding would be painfully slow. My 6100 running MusicMatch Jukebox back in 2002 took the better part of an hour to encode 45 minutes worth of music at marginal quality.