Can MFC applications with Ribbon toolbars built under VS2010 be run on versions of Windows that were released before the ribbon was designed - e.g. XP or W2K, not just Vista or W7?
If no, what (if anything) can be done to make them work?
Yes, they will run on XP with SP3. But not for older systems, as applications compiled with VS2010 require at least XP SP3 to run (requirement of the C-Runtime library).