@BellGoRiiing: iTunes is the easiest to use, IMO... i believe it's somewhere in 'preferences' where you can set the file quality you want converted AAC-format files to be created at. Once that's set to whatever you like, highlight in your library what files you want converted, right-click, and 'convert to AAC' is what you want. depending on how many files you're converting at once, it may take a while.