Windows XP (The letters "XP" stand for e XP erience) first released in 2001, is an operating system developed by Microsoft for use on general-purpose computer systems and is known for its improved stability and efficiency over previous versions of Microsoft Windows.

The most common editions are Windows XP Home Edition and Windows XP Professional, (XP Pro has additional features such as support for dual processors )

You can buy standard versions, upgrade versions and OEM versions.
An upgrade version is an economical way of installing a preferred edition by upgrading your PC's version of Windows XP.

You can also obtain OEM versions at even lower cost, these editions are typically purchased with a complete computer system, and are identical to full retail versions but lack any packaging and offer limited support, typically online rather than phone support.

"Original Equipment Manufacturer" (OEM) hardware or software is supported by the business or system builder that uses it in the manufacturer of their own equipment.
e.g. Dell would use OEM XP software to install on a laptop, then they would then be the ist point of contact if the buyer were to experience problems with the hardware or software (oem XP) installed on that particular machine.

You can buy an OEM version of XP with an item of hardware, so you can then assume the status of "Original Equipment Manufacturer" or system builder, this means you will provide your own technical support. (Of course, you can still refer to Microsofts excellent online "help center")

Microsoft is not opposed to the practice. Rather, the company says that people who purchase OEM software will simply be expected to abide by the terms of the licensing agreements.

"The actual Windows XP part of this package has actually improved since the previous stand-alone versions of XP (home, professional etc) in many ways. Firstly, this version has already had the influence of the current Vista 'aero' look, as the taskbar, title bars, and other XP tabs fade away a lovely clean modern look, going from blue to pale/sky blue, making it look indeed aero like."

Buyer's Review for Microsoft Windows XP Media Center Edition (Amazon.co.uk)

What are the advantages of using OEM XP editions?

The software on the disc is the same as that found in any retail edition.

An OEM licence allows you to receive patches and security updates.

OEM XP editions are much cheaper than full retail versions.

What are the disadvantages's of using OEM XP editions?

OEM editions of Windows do not have elaborate packaging or manuals.

OEM software cannot be returned once opened.

OEM versions are not transferable to a new machine.

OEM software is also tied to the motherboard it is first installed on.

Microsoft says that anything is fair game, except the motherboard. Replacing the motherboard in a computer results in a "new personal computer," which is not permitted within the licensing restrictions of OEM software.

However, it has been suggested that an individual could contact Microsoft and report that their motherboard has failed when they want to build a new computer. It is Microsoft's policy to allow motherboard swaps in instances where a system is defective or has suffered a hardware failure.

* Ensure you buy Windows software from a reputable seller, and not suspect pirate software. Legal software has a Certificate of Authenticity (COA).
A Certificate of Authenticity (COA) is a label that identifies genuine legal Microsoft® Windows® software.