possible virus/worm/trojan

[cksfriday]

robin or any other computer wizard, i have a question for you? when my mom signs in to her profile on her windows xp pc, she gets these lovely pop-ups stating she has a worm/virus/trojan and she hits close and/block but a few minutes later it will pop up again and the cycle continues. when they sign in to my dad's profile, they don't get the screens.

is this really the work of a virus or spyware? what might be the best way to get rid of this?