I only have one computer
This method relies on the computer having a secondary monitor connected and being capable of using the main screen while the secondary screen is in "Full Screen" mode. This is not the recommended method due to the complexity and possibility of your output being interrupted.
This method will not work with Apple OS X10.8 Mountain Lion due to the way the main screen is obscured while in "Full Screen" mode. OS X10.9 Mavericks will work with this method.