There are 3 types of licenses :

* OEM - Only allows you to do a clean install
* Retail - Allows you to do an upgrade of existing OS
* Volume - Also known as the corporate version

The license type is contained in the install file of your Windows XP CD.
X:\i386\setupp.ini
Pid=55034000
The 5 first digits of the Pid says what license it is, and the last 3 digits says what license cd-key it accepts.

* OEM - Pid=82503OEM
* Retail - Pid=51882335
* Volume - Pid=51883270

Note it is possible to interchange the license and the cd-key which is required. Ex. one could create retail license accepting OEM keys Pid=51882OEM.

Note that one cannot change an OEM/Retail version to a corporate version by just changing the Pid. There are other differences in the files included and you will still have to activate it with a corporate key.

XP Home Edition, Media Center, Tablet PC don't have Volume Licensing version.

There is information <a href="http://wiki.lunarsoft.net/wiki/Product_IDs" target="_blank">out there</a> about the different numbers found in the PID.  I'll just copy the info here to make it easier.  PID=xxxxxyyy

'xxxxx' = Microsoft Product Code
  MPC list - English locale
[color=yellow:c73241fc0d]     * 55274 : XP Pro generic OEM[/color:c73241fc0d]
    * 55276 : XP Pro (upgrade)
    * 55276 : XP Home (?) †
    * 55277 : XP Home generic OEM
    * 55285 : XP Pro †
    * 55661 : XP Pro (retail)
    * 76475 : XP Home (upgrade) (?)
    * 76477 : XP Home Royalty OEM ‡
    * 76481 : XP Pro Dell OEM
    * 76487 : XP Media Center Edition 2005
    * 76487 : XP Pro Royalty OEM ‡
    * 76487 : XP Pro SP2 (retail)
    * 76487 : XP Pro volume license (with '640' channel ID)
    * 76500 : XP MCE 2005 (which is XP Pro with no domain capability)
    * 76588 : XP Pro x64 OEM 

MPC list - other languages
    * 55372 : XP Home - German (OEM)
    * 55375 : XP Pro - German (VLK)
    * 55677 : XP Home - Dutch
    * 55679 : XP Pro - Dutch
    * 76381 : XP Home - Danish
    * 76392 : XP Pro - Danish
    * 76396 : XP Pro (also Home?) - Dutch
    * 76412 : XP Home - French (OEM)
    * 76413 : XP Pro - French (OEM)
    * 76440 : XP Pro - Norwegian (retail)
    * 76447 : XP Pro - Polish
    * 76460 : XP Home - Spanish (Royalty OEM) ‡
    * 76470 : XP Home - Traditional Chinese (Royalty OEM) ‡

'yyy' = the Channel ID
    * 000 : Other (includes some retail, upgrade and evaluation versions)
    * 006 : MS or Partner promotions
    * 007 : FIXME : Retail
    * 009 : Not for resale - bundle
    * 011 : Upgrade (XP Home?)
    * 083 : Windows Genuine Advantage
    * OEM : OEM (This does not specify royalty or normal OEM)
[color=yellow:c73241fc0d]    * 270 : Volume License[/color:c73241fc0d]
    * 296 : MSDN
    * 308/347 : Microsoft Action Pack subscription
    * 335 : Retail
    * 640 through 652 : Volume License (usually generated via 270 CID in setupp.ini)
    * 699 : Volume Windows XP Tablet Edition
    * 071 : FIXME : Unknown.

If one wanted to find a torrent of an untouched and unmodified XP Pro disc, do a search at teh pirate bay for &quot;Microsoft Windows XP Professional Corporate Edition RTM SP0 2001&quot;  You can then get SP3 for XP from <a href="http://www.microsoft.com/DownLoads/details.aspx?FamilyID=5b33b5a8-5e76-401f-be08-1e1555d4f3d4&amp;displaylang=en" target="_blank">Microsoft</a> and run it after installing XP or <a href="http://www.howtohaven.com/system/slipstream-xp-service-pack-3.shtml" target="_blank">slipstream</a> it before installing.  The PID numbers in yellow above match what's on the RTM SP0 disc I mentioned and works out to &quot;Windows XP Pro Volume  	WXPVOL_EN  	23-08-01 8:00  	55274  	270&quot; from the site linked above.  Another good PID (meaning it works with the student key and needs no cracks or other bullshit to get updates or pass WGA) is Pid=76487270 - taken from an SP2 disc I've used over and over on several different machines over the years.