help with removal of "SECURITY ALERT POP UP"

[alligatorman]

 Can anyone advice me how to remove a pop up on my screen which says "security Alert" As soon as i go into my email, this pop up would appear and it reads.

SECURTY ALERT;

The security certificate has expired or is not yet valid.

I dint know if this is caused since i have just reinstall the windows xp program. Its annoying and would like to remove it from my screen. To remove it when it appears constantly  i need to enter YES ! Yes! Yes!.
Any help appreciated.

Thanks 

Alli

[SuperDave]

Hi Allie, your thread has been moved here because it is believed that you have a virus or malware on your computer causing your problem. Could I ask why you re-formatted? Were you having problems? To begin with you should go to this thread and follow the instructions to the letter.
http://www.computerhope.com/forum/index.php/topic,46313.0.html