Waylander the Slayer said:
Forget all these settings and start with a small village or town and slowly you can build up from there as based on player actions. KISS is invaluable for being a good GM.
This is my recommendation, too. If he wants a full world map, there are a few sites around that will generate a fractal globe. I think there's one at the Irony Games site (but I'm not sure). From experience, I can tell you that starting small is one of the best things a creative DM can do -- you build the history as you go.
If he really wants a pregenerated setting, my first vote would be Greyhawk -- with just the Gazetteer. It is intentially designed to allow the GM to flesh it out. And it
is D&D. Anything core is appropriate to Greyhawk.
Barring that, I'd go with Eberron. There is only one book for it, right now -- that's about as low of product history as you're going to get. There is a bit of new crunch, but most (new races, new class, new critters) fall into the category of not being new rules, just new constructs within the existing rules. Dragonmarks and action points are the only truly new rules, and neither is complex nor required for play. A tip on using action points, though, is to track them by handing out poker chips or tokens to the players, rather than marks on paper.
I'd stay away from FR. Part of that is personal bias, but part is because it is a huge setting with a lot of history and many books. It has a few new systems (spellfire, IIRC) in the core book, too.
I've never opened a Kalamar book, so I can't comment. It might be a great choice, though.