When installing an EPiServer CMS 4 (using EPiServer Manager on a machine that has .net Framework 3.0 or higher installed the installation manager fails.

In order to make the installation complete, rename the folders containing the framework files for 3.0 and higher (typically "C:\WINDOWS\Microsoft.NET\Framework\3.0") to a different name during install (simply adding an underscore in the "3_0" folder name does the trick).

PS! Remember to rename folders back to original names afterwards.... :-)