Slowing Down Of Pc

After installation of Bitdefender internet security 2013 my desktop PC has slowed down drastically.To open documents like word and power point it takes a lot of time. VLC media player is not functioning now. Also while accessing internet through google chrome or mozilla the browser is responding very slowly or is giving the message "aw snaps" or crashed etc.Its not the problem with internet connection since i'm able to access the same through tab and laptop(in which no security system are installed). Initially i was having K7 anti virus in my desktop PC and it got expired.No such problem existed while using the same for last 7 years. This is the first time i've gone for this product and its giving a lot of problems.Any means of directly speaking to some service support personnel.