On a second note, I doubt very seriously that .Net 4.0 performs that much faster than .Net 3.5. More than likely you are seeing performance improvements because some part of AC calls an API that does not exist in .Net 3.5 but does in .Net 4.0. However, the point still stands: If .Net 4.0 is required then AC should install it for you or at least give you heads up.

JamesNT

James Summerlin
My personal site: http://www.dataintegrationsolutions.net
james@dataintegrationsolutions.net