In a statement to CVG, Valve said Steam users will have to update to Windows XP Service Pack 2 at the very least if they’re to continue receiving Steam updates. Fortunately, Valve says less than 1% of its 40 million active members are still using Windows XP SP1.
This requirement most likely won’t apply to the majority of you reading this. Microsoft released SP1 way back in 2002. SP2 was released in 2004. Even if you’re still running Windows XP, you’re more than likely running the latest service pack even if you don’t know it.