You can't change the Ms Flag until you've actually compiled a *.img file using either MapSource or MapInstall. Don't mess around with any other IMG files in the PC installed map data. Once the installation is completed you can make [compile] a *.img file and then change it's MS Flag with either GMapTool or ImgTool. Please read the first few posts of this thread carefully, if you have 64 bit OS you may need to modify the install file as suggested in Post #4.