IMG is disk image-file. It's the same as a .DSK file, except for the first byte, which is a header-byte.
 If you delete it, it's exactly a .DSK file.
 
 [These information found at http://www.faq.msxnet.org/suffix.html]
 
This program by Sean Young converts a IMG disk image to a DSK one.

source code taken from:
http://www.funet.fi/pub/msx/othersys/img2dsk.c

Morphos conversion by Fabrizio "Lanch" Bartoloni (lanch@tiscali.it)

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                 3944    9840  40.1% -lh5- 0d81 Jun  7 22:15 img2dsk/img2dsk
[generic]                  837    1977  42.3% -lh5- 675f Jun  7 20:06 img2dsk/img2dsk.c
[generic]                  377     651  57.9% -lh5- a7d6 Jun  7 22:54 img2dsk/img2dsk.readme
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         3 files    5158   12468  41.4%            Jun  9 19:03