I think it might stretch if one were wide screen and the other not wide (3x4).
 
The best software for multi monitors is Ultramon. I've used it for years. I think they have some sort of free version now, but i paid the 25 or 30 dollars for the full version. I am the IT tech for a travel agency and all of our agents run dual monitors and ultramon. When they have a client in front of them, they put their monitors in mirror mode with a single click, then spin one of the monitors toward the client and they both view the info the agent wants to show.
 
Realtime Soft UltraMon
 
 
Oh and for what it's worth, i'm disappointed in the things taken away from us in Windows 7.    If i were not an IT tech i wouldn't buy it.    Just like many...