don't do anything with the PES2010_OPTION file. that has nothing to do with it. leave the one in there that you had on there from your xbox 360. all you need to copy from the downloaded OF is the EDIT file and all of the UNIFORM files do not touch anything else otherwise it wont work.
that is just what i did, but the xbox doesnt read the usb anymore and says i must reconfigure it again. i don't know why.
should i try different usb?
EDIT: actually, i forgot to do something crucial. I didn't copy the original save files to the usb, i just loaded PES and told it to use the usb as a new save. I should copy the hdd save files first and see if it works.