It's most likely not the video drivers! Upgrading your drivers may in fact make MTW unplayable if you have a GeForce video card, as the latest drivers seems to cause the game to crash a lot.

I have had good results lowering the DirectX memory set aside for textures. On older GeForce drivers this setting was available directly in the Advanced section of the driver setup (a value of 8-16 MB was usually OK). On newer drivers this explicit option has disappeared, but there is a general "Performance and Quality Settings" section. I've improved my performance by changing this setting from "Quality" to "Performance".