I just reviewed the update history on my main office PC.  It was placed in service in June 2006 and runs XP Pro.  I wanted to check the update history after the most recent flurry of “security” updates.  So I got curious to see how many it has had in total in the 3+ years it has been in service.  There’s the answer 380.  If it had been older the number would have been even more since this one was commissioned after the release of SP1!