Thanks. If I understand it correctly the binary file is the one I can get from the EPROM, as it is a Stage 3 and is going to be altered, and the definition file, (.xdf) is the one that shows the location of the maps and works in conjunction with the binary. I have put my standard chip in to the reader but it can't read a 27C64 chip (old technology). However when I put the new blank chip in, which is a 27SF512 it reads it fine and everything seems to be in the right place but as this .xdf file is for a green engine and mine is a red engine am I missing some maps or have I too many! Remember I am still learning just like you guys did when you first started.