Anyone have these or at least know what type of file they are? I klnow they are an pre-existing format- not sure what though.

the files have a .krk extension

or buy them here

http://www.xboxkaraoke.com/index.cfm?&set_flash=0&default_language=English

Did you read the thread about the playstation media centre? It will also work with the Xbox and then you can use the DVD karaoke discs and have echo, just another way of doing it.