I have a TFS 2008 Build Agent that has been used to build .Net 3.5 applications. I now have a .Net 4.0 app which i want to compile on the same build agent. I have ensured that MSBuild 4.0 is installed on there and all the required componentry is also installed, but i am getting the following MSB4062 error when building:

[Any CPU/Release] C:\Program Files\MSBuild\Microsoft\VisualStudio\v10.0\WebApplications\Microsoft.WebApplication.targets(244,5): error MSB4062: The "Microsoft.WebApplication.Build.Tasks.GetSilverlightItemsFromProperty" task could not be loaded from the assembly C:\Program Files\MSBuild\Microsoft\VisualStudio\v10.0\WebApplications\Microsoft.WebApplication.Build.Tasks.dll. Could not load file or assembly 'file:///C:\Program Files\MSBuild\Microsoft\VisualStudio\v10.0\WebApplications\Microsoft.WebApplication.Build.Tasks.dll' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded. Confirm that the  declaration is correct, and that the assembly and all its dependencies are available.

I am presuming that i get this because the TFSBuild.proj gets executed by MSBuild 3.5 which in turn means my solution is compiled with MSBuild 3.5.

Am i correct with my diagnosis? Is there any way to ensure that TFS2008 uses MSBuild 4.0 for my solution? Can it be done on a single team project so that it doesn't affect any other team projects being built on the same build agent?

Note that i have checked the question Build failing - VS2010 solution on TFS2008 and this is not a duplicate.

Thanks :)