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This error basically means that the product key used to install Windows on your PC is not recognised by the Windows Genuine Advantage validation tool. Just recently, Microsoft started issuing a Windows update that causes the WGA setup process to appear during boot (if not previously installed). If you go through this setup process and if this finds a problem, it will display this message after the next boot.
Have a look at the bottom of your laptop to make sure it has a Windows XP product key. If this sticker is not present, I would strongly recommend getting on to the shop you bought the laptop from as quite often this message means that the reseller has installed a counterfeit copy of Windows on the PC/laptop, especially when the Windows product key sticker is not present on the PC. In the meantime, you can try doing a system restore to a day before you recall the WGA setup screen appearing to see if this gets rid of the message.
If the product key is present, try updating the Windows XP key on your PC to this. You can find steps here.