You probably need to add the path of your pip installation to your PATH system variable. Pip is installed at C:\Python34\Scripts\pip so pease add this path to your PATH variable.
To cross check if it is already in your PATH variable, please type echo %PATH% at the CMD prompt
To add the path of your pip installation to your PATH variable, you can use the Windows Control Panel or the setx command as follows:
setx PATH "%PATH%;C:\Python34\Scripts"