I am very confused by your question; you don't seem to understand the basic workings of a computer.
An operating system is a program which runs all the time after you boot up. It watches the keyboard and the mouse and waits for you to tell it what programs you wish ro run. Windows XP is an operating system, so are Windows 7 and Windows 8.
You tell your computer what you want it to do, usually by clicking on an icon or typing a command. Doing that will start a program running eg, photoshop to edit photos, Word to deal with documents, Excel to work with spreadsheets etc.
If you want to use the internet you need to run a program known as a browser. Firefox is a browser, so are Internet Explorer and Chrome. You tell the operating system that you want to use the browser by clicking on an icon on your desktop or typing a command.
Can you please tell us again exactly what you are doing and what will not run? With the information you have given us I don't think we can help you.