Not sure exactly what radio model you have.. I have the Estone 8500 P.O.S - limited documentation edition:
Some observations:
Max size USB thumb drive is 4GB...
Any size larger will not work...
It appears to play divx encoded AVI files on my USB thumb drive...
Don't expect HD or perfect playback... It will occasionally get fuzzy or pixelated...
I use DVDFAB to rip my original dvds to files or disposable dvd copies. DVDFAB.com
There is a "digiport" on the front - have not been able to find out more or order cable for this...
Good luck. If anyone knows anything else please contribute to this thread...