How to fix the pop up on windows xp

[Beatlejux]

Hello, My Mother has gotten one of those popups on her computer screen that keeps telling her tha her computer is at risk and to do this and that, then wants her to pay for the service to protect her computer...we've all had them and it pops up everytime you start windows. I used to get them alot when I had WXP but it's been so long ago that I can't remember how I got rid of it. Can anyone help me out there? Thank you so much in advance!!

 

[Emerald]

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