Hate that Pop-up’s

Dear Fellow Tech-Brains ( Help )
I used win-XP operating sys, its running in top condition no trouble what so ever, recently I got this pop-up commercial popping up left and right on a timely manner.

this pop-up window says just Portal on the menu Bar, and I get all kinds of filthy and regular commercial. Since I have 2 daughter I am so scared of this Pop-up screen. Please tell me how do I get rid of this?
Thanks a ton
Ravi