If you are using a 3.5 version of the MSBuild Extension Pack, you may choose to run 4.0 side by side or replace your installation with 4.0.
To run 4.0 side by side with 3.5, simply accept the default installation path of the 4.0 installation program, which is %PROGRAMFILES%\MSBuild\ExtensionPack\4.0. You may then target this version with any new or existing code you have. All existing code targeting
3.5 will operate as normal.
To replace your 3.5 installation, first uninstall your 3.5 version and then install 4.0, taking care to change the installation path to the path where you had 3.5 installed, e.g. %PROGRAMFILES%\MSBuild\ExtensionPack