* I agree with the suggestion that a treatment of D&D would do best as a TV series. People have mentioned "Record of Lodoss War" (which is the D&D-est thing I've ever seen) and other TV shows that do the D&D thing pretty well. I haven't seen "Legend of the Seeker," but it sounds like it's along those lines, too. Back when I was a kid, there was a very D&D-esque show called "Wizards and Warriors".
But, as has been pointed out, there are already movies of things that inspired D&D, like "The Lord of the Rings" and "Conan the Barbarian" (with a new, non-Schwartzenegger version supposedly coming out next year). If the WoW movie ever gets made, well, that's based on Warhammer Fantasy, which in turn was inspired by D&D. What I'd like to see is a Fafhrd and the Grey Mouser movie... Another influence on D&D, and one that reflects its tradition of treasure-seeking and skullduggery.
If someone were to make an honest-to-goodness, get-across-the-feel-of-the-source-material D&D movie, I think their best bet would be to make a Forgotten Realms movie (though an Eberron movie would look pretty awesome, and a Planescape movie would be fantastic), since that's been consistently the most popular published D&D setting for decades. A setting is not a story, but one could do worse than to adapt an R.A. Salvatore novel set in the Realms.
* If you're in a place where you can't obtain D&D, there are a ton of D&D clones available for free online, using the same rules-sets that older editions of D&D used, but with the serial numbers filed off. These retro-clones play like the original editions. If you really want to play some D&D, you could do worse than to go back to its roots with these. There's Basic Fantasy and Labyrinth Lord, which emulate the old Basic and Expert D&D sets; there's OSRIC, which emulates 1st Edition D&D; and I'm guessing there are probably retro-clones out there that do 2nd Edition, too... Do a Google search or surf DriveThruRPG.
* MovieBob, I'm terrible at math. I have to mentally count on my fingers (well, actually, I count imaginary dots on a die or a domino) in order to do simple math. And I've been running D&D games for over 20 years. It's not really that difficult; it just takes a little getting used to. WotC (who publishes D&D) just came out with D&D Essentials, a.k.a. The [New] Red Box, which is specifically meant to be an easy entry point for 4th Edition D&D. And if D&D is too math-heavy for your tastes (again, something I can sympathize with), there are countless other tabletop roleplaying games you could get into that use simpler systems, systems based on playing cards instead of dice, diceless games, etc. Drop into RPGnet and ask, and you'll get about a thousand suggestions to suit your tastes.