Assalm Alikum friends

Meri Drive say Achank kch folders delte ho gaye ,an kch folders k adner say file bhi delete ho gaye achanak say ,yeh dosri martba howa hai shyad virus ki waja say .jb mein k AVAST INTERNET SECURITY laga howa hai aur win 7 hai ..
koie yeh bataiyeh ga k aesa Q ho raha hai???