When I transfer it to the phone, only some of the songs work properly. Sometimes I'll have a song on there, it'll play the first few seconds, then it will say "File format not supported"" What's that about?

What do I do?

there is a problem with different moto fones ,these fones do not support many sound formats like wav etc,jus check yr fones manual for compatibility,n aft that load songs into yr fone!!