Hey, one of my friends has a 'klez worm" virus and "exploit mine.gen.mme" or something like that.

He's just going to get Mcaffee anti-virus. Is that all he should do or is there anything else to help his computer/hard drive/files?

First, and I'll probably get a lot of flames for this but, they should
really get Symantec Norton Anti-Virus. Much more user-friendly
and for the most part automatic and unnoticable. I have worked
on literally nearly a thousand virus infected computers and a great
majority of them had McAfee on them. But..apples and oranges.

First, they should remove the virus first and then install the anti-virus
to a clean (virus free) machine. Some strains of virus will actually
disrupt the install or affect it in some way.

They can download the virus remover from Symantec's site:
Klez remover (http://securityresponse.symantec.com/avcenter/venc/data/w32.klez.removal.tool.html)

It's might be better to run the cleaner in safe mode. After it is clean,
that's when you want to install the anti-virus and definately update it.
You may find even more virii on the machine.

On a personal note, There is absolutely no reason that you should
not have anti-virus on your windows machine (I know).