If you're still running an old version of Windows XP on Service Pack 1, you'll no longer be able to run Steam from August 31.
Valve has announced that it will stop supporting or provide any further updates for users running on Windows XP SP1, so it's a good time to upgrade to SP2 if you've been holding out for whatever reason.
If you're reading this on XP, it's unlikely that you're still running on SP1, but you should check to see if you've got the latest version of Windows XP installed just in case.
It should be said that most games on Steam have already discontinued their support for SP1, and some titles won't even run on anything less than Windows Vista—so it comes as no surprise that Valve is cutting back its support for the old platform.
