Install virtualenv via pip or easy_install
pip install virtualenv
Make sure site_packages (C:\Python27\Lib\site-packages) is in your env path
See here if you dont know how to set an environment variable in windows
Best practice is to make a directory where all your virtual environments will live. So, maybe in your home dir,
The default python interpreter that will be used is the one that you used to install virtualenv.
To create a new virtual env, enter:
So typing "virtualenv virt1" (ignore the quotes) will create a new directory called virt1, and it will have your default python instance, easy_install, pip, its own package directory and everything else you need.
A couple of useful arguments that you can pass when creating your virtual env are:
--no-site-packages (this means give access to the global site packages in your virtual env. I think this is the right way to do it, otherwise things can get messy)
--python=path_to_a_python_interpreter (this is how you create a virtual env for a specific python interpreter, probably the most useful thing you can do with virtualenv)
Now, to use a virtual env that you have created. Just execute activate inside the virtualenv's scripts directory:
You will now see your command window change to show that you are using that virtual environment. Try using pip install some_package, and you will see that the newly downloaded package is installed in your virtualenv, and not in the main python installations site_packages/