A little academic now but may be useful for others......
Win7 ISO's used to be legally downloadable from Digital River but M$ seem to have put a stop to that. However, the ISO's are still available from DR's German outlet but I think they're only downloadable as torrents.
Only one version each of x86 and x64 need to be downloaded and the "eiconfig" file removed. A menu will then be presented asking which version you want to install. It's also possible to merge the 32 and 64 bit versions to a single DVD so a single disk can be used to install any