I thought I would mention this since nearly 60 percent of consumer PCs and almost 70 percent of business PCs worldwide still run XP. You may have not read that Windows XP SP3 is now on Microsoft's Windows Update Site. Since it is not a critical update it won't pop up in the Automatic Updates notifying you of SP3.

Warning! A word of caution for those who may have an HP computer with an AMD chipset. There have been reports of computers becoming unbootable (even in safe mode!) so if you have an HP computer with an AMD chipset you may want to forego installing SP3 until Microsoft provides a patch. Other than that specific case i.e. an HP computer with AMD chipset, it is recommended by Microsoft to update your XP OS to SP3. I installed it on my machine and everything is good to go with no apparent problems. SP3 provides many fixes and enhancements along with greater security. Your mileage may vary of course..

Best,
Mike

PS: Microsoft also recommends you disable any Anti-Virus software before installing SP3 but do so according to your own discretion.