Hello,
I do not have an Ipod myself,but both my brother and niece have the 20 or 30 GB size. I'm sure playing MP3's on them would be no problem, if we could figure out how to do it.

They keep asking me like I would know this, but they both have MP3 files on a cd and want to play these files on their ipod.

Do they have to first convert them from MP3 to .aa or whatever files Apple uses as their default playing file?
Or do they convert on the fly when you put them into the library. The easiest explanation if possible would be greatly appreciated. Thank you so much!