The .IMG files should be simply CloneCD image files and usually come toghether a .CCD file (like .cue/.bin for the BIN images).
If you have the CCD you can:
1) 'mount' them
2) burn them on a CD-RW
and extract the movie from it (ususlly it is in the D:\MPEGAV\AVSEQ01.DAT in a VCD or in the D:\MPEG2\AVSEQ01.MPG in a SVCD), maybe converting the 'riff file' into a 'true mpeg' with VCDGear. (if can extract from bin/cue directly, but for img image files probably you'll have to make dat --> mpeg or mpeg --> mpeg)