It does not matter in the end. Mint is NOT Ubuntu and vice versa. I do not
know how many times I have seen people post "Ubuntu" problems only to find
that they started not with Ubuntu, but with Mint or Ultimate. Treat them as
different distros and do not upgrade from one to the other. The only part
that I would change is the order of Mint and Ubuntu and in the second
paragraph start with a fresh copy of Ubuntu, instead of Mint.

As for getting drivers from ATI, that part is unchanged. The first place to
go is to System, Administration, Hardware Drivers once he gets Ubuntu
working. It will recommend and install the appropriate driver. If one is not
available then he could build one using EnvyNG in the repositories. Once it
is installed run Envy and it will download and compile a driver for him. I
have used Envy and it worked quite well. He could do it himself, but it is
easy to miss a step and wreak havoc on his system.

Thanks for keeping it straight, though. He is upgrading from Mint and not to
Mint. That's what I get from trying to post during an NFL break. :)