Was just curious if it was yet possible to transfer files to the Xbox's soundtrack directory and use them in a custom soundtrack? I know about ripping them from CDs but am curious about mp3s or if they need to be converted to the Xbox file designation(.wmv?)? If the box has it's own file designations, is there a program to do the converting? Thanks...

Just download the XBox Soundtrack editor here and the program takes care of everything for you, including uploading the new soundtrack to your box. And by the way, yes, you'll have to convert the mp3's to WMA format before you can make it into a soundtrack. Just use a program like Advanced WMA Workshop.