lost start button and lower taskbar

I cant remember what i have done,, but i have been behind this pc so much i’m over looking something i fixed before. xp home–os—i changed some setting on my pc then my start button, start menu, and complete lower task bar disapears and it has wulpped me bad ..i also think i have a virus i cant get rid of… But i know you guys can tell me what to do.. thanks ,,,trav3850 (trav3850@bellsouth.net)