iTunes can convert M4A (or rather AAC) to MP3, AIFF, WAV, Apple Lossless and vice versa in all directions. The Windows Version can also convert unprotected WMAs to the mentioned formats (but not vice versa).

----

i herd that m4a/mp4 is an riaa scam
im just repeating what sombody told me

OMG!

m4a is so new

Yeah, only >5 years.

Next time verify your sources!