Do you happen to have the links you mentioned Neil? Cuz having a single disc with all versions of XP, Vista and 7 separately sounds good to me.. just curious is all Neil..
Alas, I was supplied with a disc by a friend who had actually torrented it- the disc I have has all the versions of just windows 7 ( you'd be better off with separate discs for XP, vista & 7, I don't think you'd fit all every version of each OS onto one disc ).
Every Windows 7 DVD contains every version of Windows 7 , it is just restricted by one configuration file : http://www.anandtech.com/show/3564