In Windows Xp, you can install two windows on the one hard drive of one particular computer. If you have two different operating systems, then you end up with dual boot system when you restart your Windows Xp computer. Also, dual boot system can be used to have Windows Xp, and operating system Linux installed on the similar computer.

When you restart your system, and you acquire a selection of two operating systems, you should prefer the one you want to keep installed on your machine.
Once the start up process is done, and your computer is prepare to accept tasks to perform certain functions, you click on the "My Computer" icon and locate the hard disks, removable storage devices .

In the hard disk box you should see two drive icons, like "C", "D". If the copy you installed later want to be cancel, it must reside on the "D" part of the hard disk.
This is due to the "C" is where you first copy of the Windows Xp resides, and it is the one you want to keep installed as the only copy on your computer.

The way you should get rid of the "D" copy is to format the "D" part of the hard drive. only right click it, and select format. This will delete the Windows Xp copy you don't need.