How to install WP 8.0 SDK if WP 8.1 SDK is installed?

I have the Windows Phone 8.1 SDK on my dev pc installed together with VS 2013. I need to open some WP 8.0 projects in VS 2013, but I can't do that without having WP 8.0 SDK installed.

However, when I try to install it from the local ISO, I have the following installation error:

** Setup Blocked **
The product version that you are trying to set up is earlier than the version already installed on this computer.

Do I need to remove the WP 8.1 SDK just to install WP 8.0 SDK and then install WP 8.1 SDK again? Is this the only way, and will it really help?

It seems I need to install the older SDK as I cannot launch my WP 8.0 projects because of this error I get when I open them:

 

Modify the VS2013 install in "Program and Features" and select "Windows Phone 8.0 SDK".