The solution you show works for a single console session, but that's likely not what you want. Its better to update the system PATH so that python is always available.
In windows, it is common to install python with an installer (an exe or msi) from python.org, activestate.com, or other site. That installer likely setup the path for you. After install, open a new command prompt and type 'python' to see if it works. If it does, you're done.
If that doesn't work, you want to update the path in Windows System Properties. There are various ways to get there, but usually pressing the Start button, right clicking Computer and then navigating to Properties >> Advanced System Settings >> Advanced >> Environment Variables >> System Variables >> PATH will do it. Just add ";C:\Python27" to the end of the existing path statement.
But be warned: If you mess up the system PATH variable your computer is basically hosed.