tech gurus! im having a little problem with one of my notebooks..

this has been happening for 2 weeks now. whenever i shut down my system it takes a couple of minutes.. like almost 2 mins... laging lumalabas yun ending ccApp... ano yon? so i just leave it alone i dont want to touch anything or butingting anything... how do i fix that? whole day connected sa net yun computer i share the computer with another person to so paper works and surf the net... maghapon nga pala nakaon ang pc and maghapon din naka connect sa net... may norton internet security 2006 naman ako.. virus kaya? running on windows xp media edition

merci d'avance!