Starting August 31st, Steam will no longer be supporting Windows XP SP1. According to Valve, this change will affect less than one percent of Steam users.
Quite frankly, I’m surprised that those running XP SP1 are even able to get Steam to boot. And if you’re part of the one percent, it’s high time for an upgrade to at least SP2. It’s okay to turn on Windows Update from time to time… it won’t bite.