If you have a computer made by a big manufacturer, like HP, Dell, Acer etc.. You can use the System Restore/Recovery option outside of Windows. They don't actually ship the CDs anymore; rather, the CD is contained on your hard drive.
When you first turn on your computer, you'll see the BIOS screen with your manufacturer's logo on it (or some technical mumbo jumbo). To access your manufacturer's system recovery option, you usually tap a certain key (it usually says what key to press on the screen). Keep in mind this may delete all of your data, as it is will reinstall a fresh copy of Windows. Some manufacturers also include a repair or backup option.
Again, this is done outside of Windows.. You'll see this screen before you see the Windows logo appear when you first boot your computer. It's just a matter of tapping the right key.
If you have an HP, Dell, IBM or Gateway it is probably F11.
If you have a Sony, it is probably F8
Anything else will probably be F8, F10 or F11.