Ummm, this is where I get befuddled by the jargon! so bear with me...

I used to use my defunct one for things like:
uploading my music onto Myspace (I think they only accept mp3s)
or making a ripped track smaller (so someone I send it to doesn't moan at me for clogging up their mail inbox)

This kind of thing? not sure whether I would do it the other way round - why would one convert from mp3s and make a bigger file??

Do please educate me!

Many thanks for all suggestions so far.

Sue