Windows XP Key or Windows XP Serial Number

Installing Windows XP requires the Windows XP Key or Windows XP Serial Number.  Depending on what version of Windows XP you are installing this Windows XP Key may be used to simply install Windows XP or the Windows XP Serial Number may be used to activate Windows XP by phoning home to Microsoft. 

Retail Windows XP Keys

Windows XP Keys are located on the CD sleeve or inside the retail packaging.  You'll want to save this Windows XP Serial Number in case you need to reinstall Windows XP later. 

OEM Windows XP Keys

On computers that came with Windows XP this is called a Windows XP OEM key and the Windows XP OEM key is located on a sticker on the case of the PC.  Make sure this sticker is not lost or damaged as you would need this Windows XP serial number if you need to reinstall Windows XP.  Windows XP OEM keys generally do not need to phone home to Microsoft making your install of Windows XP OEM easier.  Remember use only the Windows XP key that came with your CD or on your OEM sticker.  Windows XP keys you may find on the internet are not legal for use to install Windows XP.