Ok, I've tried everything here and on other forums but you guys are the most recent and most competent so far. The only thing I couldn't do was the AGP texture acceleration, I couldn't see where in DxDiag to turn it off.
When I click 'New Game', it loads for about a second on the loading screen then says Fallout3 has encounted a problem.. blah blah. I've uninstalled my Combined Community Codec Pack, patch, .NET 3.5, start without launcher, updated video drivers.. etc.
Running on a Dell Studio 17, 2.0 Ghz CPU, 4gb Ram, and Intel Series 4 graphics.. which might be the problem but I don't see why, it has plenty of memory. I also haven't contacted Bethesda support directly yet..
EDIT: Now that I looked more thoroughly at the support page, I doubt my onboard is supported. But I can run things like Sins of a Solar Empire and EQII with no problems at all.