I installed the Elecard decompressor (learnin' the lingo!) as suggested on the Help2Help link and Mpgs now Ok! Hooray .... thank you both for your help.
Incidentally if anyone else needs the elecard download the link to download it on their site is currently misdirected and leads to the download of another of their products - it's currently available directly at
http://www.elecard.com/ftp/pub/mpeg/...c_2.1.4316.zip