Wine Missing MFC420.DLL? Try winetricks.
I've been firing up my old copies of Sim Tower and Yoot Tower to, um, research for pyTower. It's been a while since I used wine, so when Yoot Tower borked because of a missing dll ( MFC420.DLL, natch ) I hit the Google and found this great little ditty: winetricks. It's a little script that will install all kinds of DLL's on demand from all over the net.
It even has a GUI!
It did the trick really fast, so I'd recommend it net time you get stuck.