I am aware that Microsoft ended their update support for Windows XP.
I am now finding a yellow shield popping up next to the clock in the right hand corner and a message is inviting me to install updates. Can this be genuine and where is it coming from? Here is a screen shot of the message
According to the latest issue of ComputerActive mag. MS have issued a fix for a zero-day vunerability in Internet Explorer 8 for XP so I would think that it is that and I think you'll be safe enough to let it install.