1203: file <filename> is not a valid .EXE file 
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  This message indicates that the specified file does not have a valid
  .EXE file header, thus the Blinker internal overlay cannot be located
  within the file.  This indicates that the file has become overwritten
  by another file, that the PATH has changed so that an alternative file
  of the same name is found instead, or that the .EXE file has become
  corrupt.