Product Activation Overview
Microsoft Product Activation is an anti-piracy technology designed to verify that software products have been legitimately licensed. This aims to reduce a form of piracy known as casual copying. Activation is quick, simple, and unobtrusive, and it protects your privacy.
Product Activation works by verifying that a software program's product key has not been used on more personal computers than intended by the software's license. You must use the product key in order to install the software and then it is transformed into an installation ID number. You use an activation wizard to provide the installation ID number to Microsoft either through a secure transfer over the Internet, or by telephone. A confirmation ID is sent back to your computer to activate your product.
The installation ID number includes an encrypted form of the product ID and a hardware hash, or checksum. No personally identifying data is included or required. The confirmation ID is simply an unlocking code for the Windows XP installation on that particular PC.
If you overhaul your computer by replacing a substantial number of hardware components, it may appear to be a different PC. You may have to reactivate Windows XP. If this should occur, you can call the telephone number displayed on the activation screen or in most instances do it over the Internet to reactivate the OS.
How long does this go on?
RETAIL VERSION
The license for a retail version of Windows XP is in perpetuity. You get to use Windows XP forever, if you choose.
But Microsoft recognizes that machines do get upgraded. If, following the activation after setup, you do not need to contact the activation center for 120 days (any changes you make during this time being seen as acceptable when the system boots), then the sheet is swept clean and you can start again using the current hardware as the new baseline to make more changes.
If you get a new computer, you are entitled to remove Windows XP from the one that is being junked, and install the same Windows XP on the new machine ? but you will have to do the reactivation by a voice call and explain (unless, as was just mentioned, 120 days have passed since the activation was last performed).
Microsoft has said that if it ever becomes not worthwhile for them to keep this activation system going, they will take steps to allow users to disable it.
OEM versions
Restrictions of specific license types may limit the foregoing. OEM versions of Windows XP are licensed together with the hardware with which they are purchased, as an entity, and such a copy may not be moved to a different computer. Also, other specific license types (e.g., Academic licenses) are handled in different ways. These are not?t a WPA issue per se, but rather an issue of the license for that purchase, and therefore outside the scope of this discussion of WPA.
There are two versions of OEM Windows XP systems. One can be purchased separately, with qualifying subsidiary hardware, and installed with that hardware to an existing machine, to which it becomes bound. The software may be reinstalled and reactivated indefinitely as with a retail system as long as it is still on the original machine. It may not be transferred to a different computer. It is activated as described above, but if it were installed to hardware seen as not substantially the same, the activation would be refused as falling outside the license.
In the other OEM form, the system is provided pre-installed by a major supplier. Instead of activation, the system is ?locked? to the BIOS on the motherboard. The validity of this lock is checked at boot. As long as this is satisfied, other hardware may be changed freely, but any replacement motherboard must be for a compatible one supplied by the original maker.
If a BIOS-locked system is installed to a board where the lock fails, it enters a normal Activation process at startup. However, beginning 1 March 2005, the Product Key supplied on a label by the computer manufacturer, and used for the initial installation, will not be accepted for activation. A new copy of Windows XP, with a license allowing installation on a different machine, will be needed. This means that any replacement motherboard (or upgrade to its BIOS) must be supplied by the original maker, who will ensure the lock is maintained.
Product Key overview
What you need to know about your product key.
For years, Microsoft has (quite legitimately) been concerned about piracy issues surrounding its products. In an effort to combat this, it came up with the concept of Windows Product Activation(WPA). When you install Windows XP on a computer, you must enter a 25-digit code from the original Windows XP CD during Setup. Setup takes this information, mixes it with information it derives from the hardware configuration of the computer, and creates a code that it sends to Microsoft to validate the installation. While it is true you can use any valid key to Install/Re-install or Repair Install win XP(You cannot cross keys from home to pro or vise versa as the install will not accept the key), you will run into Activation problems with Microsoft because each product key can only be in use on any one computer at any one time. After the key has been activated, it can?t be used on another computer unless you?re using a Volume-Licensed version of Windows XP. That means each Windows XP computer must have a different product key.
If you try to reinstall Windows XP and don?t have your original product key or CD, you cannot simply borrow one from another Win XP computer. Normally, you?d have to buy a new product key from M.S or purchase a new copy of Windows XP. Naturally, you don?t want to do that because you already have a copy of XP?you?re just missing the valid key that goes with your copy of XP. That is why you must keep your product key in a safe place, if the key is lost and assuming you can still boot to Windows these small utilities will decode the key for you.
http://www.magicaljellybean.com/keyfinder.shtml
http://www.michaelstevenstech.com/ViewKeyXP.htm