I know someone won't like this 'possible' solution, but Why don't you just uninstall .net 1.0, uninstall .net 2.0, and after a restart, try to install .net 3.0 (it will install .net 2.0 + WinFx) .net 3.0 can run applications developed on .net 1.1, 2.0 and 3.0.