As much as I would like to think that each and every one of you is more than ready to say goodbye forever to your old operating system and hello to Linux, I know that for many this is a very big jump. If you are still feeling a little insecure about simply breaking free and running Linux, I'm here to tell you that you can get the best of both worlds. It is called dual booting.
Dual booting refers to the technique of making a home for both operating systems on your machine. When you start your computer, a small program called a boot loader offers you a menu of choices from which you can decide to boot Linux or whatever other operating system you have installed. That boot loader, for the most part, is called Grand Unified Bootloader (GRUB). A second and still very common boot loader is called LILO, the Linux Loader.
When you load Linux on a system that already has Windows installed, your new system is smart enough to recognize the existence of this other operating system. You'll find that an entry for both your operating systems will magically appear in your boot loader menu.