XP is very picky but, it is the computer configuration and product key number that is the most important for activation. Are you including all of the original CDs?
Many older versions of Microsoft's software don't require activation so transfering ownership from one person to another isn't a problem.
I know with Dell, you can transfer ownership if you sell or give the computer to someone. Whether that is really necessary, I don't know. But each time I sold or gave away a Dell, I transfered ownship to the new person.
I am going to sell my notebook. After clearing out my hard drive, can the buyer use my OEM MS operating system via its Recovery Disk ? Will MS accept the changed registration ? Will MS accept the changed registration for other software such as Word or Nero's Vision Express ? Can software only be used by the original purchaser?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic