Installing .net framework 2.0 will ovewrite the version 1.1?

When you install the .NET Framework, two different types of configuration files are installed, machine configuration files and security policy configuration files. In a side-by-side installation environment, you can install multiple versions of the .NET Framework on the same computer. Each installed version has its own set of machine configuration files and security policy configuration files. The settings in these files are specific to the version that installed them. https://support.microsoft.com/kb/815441 which means, installing .net framework 2.0 doesn’t overwrite the version 1.1

When you have two different versions of the .net framework, the application will automatically choose the latest version of .net framework. In order to target on the older version, you can use an application configuration file to specify which versions of the .NET Framework an application or component supports. Visit this article https://msdn2.microsoft.com/en-us/library/9w519wzk(VS.80).aspx to learn how to use an Application Configuration File to Target a .NET Framework Version.

To understand more on installing Visual Studio Side-by-Side, you may look at this: https://msdn2.microsoft.com/en-us/library/ms246609(VS.80).aspx