Thanks Dan.  Funny, I just talked to the Support Center and was told that multiple versions couldn't be installed at the same time.  I'll get some confirmation with the customer that it works and then let the Support Center know so they can update their knowledge base.

It should be possible, but CF3.5 is very large, so you may run out of room if you try to load both plus some apps.  If they haven't tried yet, they should try running their 2.0 app on 3.5.  Some of them will run fine.  I have a customer running his CF2.0 apps on a  CE 9090 with CF3.5 with no issue, but the apps are fairly simple. You will see some stuff in these links about using .config files.  I don't think you will need to do that, but I have tried them going from 1.0 to 2.0, and they did work. http://blogs.msdn.com/b/andrewarnottms/archive/2007/08/27/reflections-on... http://msdn.microsoft.com/en-us/netframework/bb986636