please help

hello everyone i am new to all this so please bare with me,i have a macbook which i bought on the 23/8/2009 and a hacker or some thing seems to be in it .firstly most of the apple files have been changed to com.apple,i cannot use the wifi because it will not connect i cannot download the quick time and everytime i boot up it is doing it from the dvddrive and it is using a dvd by the name hl dt st dvdrw gs2w.also if i go into finder and places the one with my name onwhen you open it the files has no favicons just a square white box.i have been told it could be aport hacker or attacker i am not sure this is the first time i have had a mac so i am not familiar with them.i would be grateful for any help.thanx ladyvel

did you buy new?