MX 420 here, and I can only say what I did myself.
Before installing:
Switched video drivers twice, first to 81.85, then after seeing some reports of problems in the forums, to an earlier version (the one from April 14, 2005). Complete uninstall and reinstall both times.
Defragged the hard disk.
Downloaded the version of DirectX 9.0c that comes with the game.
Before playing:
Reboot the system.
Turn off all unnecessary peripherals and practically empty out the system tray.
Problems I still have after all of that:
The bread-only and related graphics bugs, which I suspect can't be fixed except possibly by a patch.
Stuttering of the opening movie. (But in-game wonder movies seem to be fine -- I haven't built any in the very late game, though.)
Weird graphical glitches and random slowdowns if I try to alt-tab out of the game to do anything else, or if I restart the game again after quitting but before rebooting. Also one CTD in such a situation.
Lately, a major hang at the beginning of each new session. Loading goes fine, but as soon as I hit end-turn, the game hangs for a while -- about five minutes is the longest so far. Play appears to be normal afterwards, though. This may be related to me being lazy and not shutting down my firewall and my internet connection prior to playing over the last day or so (because it's oh-so-difficult to disconnect the router (

at self)). I'll have to check again tonight to see if that is in fact the source of that problem.
Anyway, assuming I do all of the above, and acknowledging the graphical bugs, the game seems to run just fine indefinitely (I've played only up to about four hours at once). No crashes, no hangs, no problem zooming out (within reason; I've never gone beyond where you first see the clouds), wonder movies run ok, diplomacy is ok, and inter-turn speed is acceptable (only standard-size maps so far for me). I haven't tried turning on the grid, as I've heard that's very graphically intensive to switch on and off.
Hope some of this helps someone.