I'm running M&B (and many other games) in W7.
Currently, I struggling with "unable to lock vertex buffer" type errors, but I don't think its W7 issue (though, it could be).
Other games aren't having this issue.
I just read someone else's post that indicated that it could be related to "dream scene" for Vista users... and W7 has a "slide show" for the background that I was using. So... I'm just turned that off, and I'm going to see if that's the issue.
Scratch yet one more idea. Nothing so far has helped. I have dropped every setting to the bottom, except for battle size. If I use a battle size over 150, it crashes. It never used to crash under Vista x64 same video card(s), but on my old PC (I was using a core 2 quad Q6600, now I'm using a i7 920 quad).
So far my machine has handled everything else I've thrown at it with aplomb. But m&b is just unhappy! And M&B without the large battle size is just not the same... its not the game I fell in love with.
Hopefully something shifts in the near future... but for now, I'm going to have to play something else.
In general, everything has worked beautifully in W7... which is Vista, after all - very, very few changes have been made in terms of the device drivers, etc. In fact, I'm not sure any changes have been made at that level - mostly GUI stuff.
G/L