When I first introduce a former Windows user to Linux, a stable version (currently version 8.04LTS) of Ubuntu is usually a good place for them to start.
My latest "convert" downloaded an .iso file, as requested, but when I asked him for the md5sum number so we could check for file integrity, he informed me that Ubuntu doesn't have any. I checked the Ubuntu downloads page, and... no md5sum listings.
(plus, only versions 10.04LTS and 10.10 are available to download; but when you read the fine print elsewhere on the site, Canonical recommends version 8.04LTS as their "productivity" release. New Ububtu-brand laptops ship with version 8.04 loaded)
So, how do we check for .iso file integrity before burning an Ubuntu operating system disc? Not possible, apparently.
Consequently, I loaded Puredyne version 9.1.1 on this fellow's computer and it is running flawlessly.