The long-standing bug with hibernation in Windows XP SP2 has finally been fixed. The bug, affecting machines with more than 1GB of RAM, would prevent a machine from going into hibernation. While the article doesn't mention it, the bug didn't affect all users and as such Microsoft never felt the need to release an urgent patch. Now, however, assuming you pass WGA, you can get the fix yourself. If you have this problem, most likely you're using a notebook. Hibernation is very nifty and a great way to keep multiple programs open and not have to reboot a machine every time you want to save power, so having it work properly is fairly paramount to a mobile Windows workstation. If you already happened to be using hibernation with 1GB or more of RAM, you're obviously not affected and can probably ignore the update.