You need to install that library, if you're on windows which it seems because of your "C://" first install setuptools.
https://pypi.python.org/pypi/setuptools
Using Windows 8 (which includes PowerShell 3) or earlier versions of Windows with PowerShell 3 installed, it’s possible to install with one simple Powershell command. Start up Powershell and paste this command:
(Invoke-WebRequest https://bootstrap.pypa.io/ez_setup.py).Content | python -
You must start the Powershell with Administrative privileges or you may choose to install a user-local installation:
(Invoke-WebRequest https://bootstrap.pypa.io/ez_setup.py).Content | python - --user
If you have Python 3.3 or later, you can use the py command to install to different Python versions. For example, to install to Python 3.3 if you have Python 2.7 installed:
(Invoke-WebRequest https://bootstrap.pypa.io/ez_setup.py).Content | py -3 -
Once installed run as follows:
easy_install semanticnet