windows xp start menu

Okay so my computer got hit with some type of virus so i reinstalled windows xp on my computer and purchased Norton Antivirus which cleaned up my computer.. A few days later my Windows start menu on the bottom left corner dissapeared. I have tryed the system restore and that did nothing, And i also tried goin to the taskbar icon in the control pannel. I clicked on it and for some reason it didnt work. I notcied all the other icons in the control panel worked. So if anyone can help me please do it would be very much appreciated thanks.