Greetings, Forgive me for asking what I felt I would be able to find on my own. I'm having some difficulty with finding a grand and combined total figure for the total number of Windows XP OS units ISSUED (sold) worldwide. A combined figure that includes all TYPES. OEM, HOME, and PRO, versions. The best I can find is a vaugue figure of 400 million, but I' for some reason believe it's higher than that. I believed they ceased production in 2008. If anyone might have a clue, I would be most greatful for your answers and input. This is for an essay I'm writing. Sincere regards- CharlesI'd contact Microsoft and see if they could give you an answer. If you MENTION to them that you are a college student working on a project they might give you the time of day to give you factual information for your project.

MS sells licenses and so they have the best accountability for "legally licensed units" running it. There was a problem about mid life of XP though where someone created bootlegs and a key activation script and distributed this through the black market making even more systems run it with illegal unlicensed OS. This was one of the reasons why they created the Genuine Advantage Tool ... more info here on that: https://support.microsoft.com/kb/892130

Best of luck on your HUNT for info, and if Microsoft gets back to you with real numbers, please report that info back here so someone else may find it on a google search.