How can i get rid of malware on my windows 7 laptop?

im cleaning it with malwarebytes and it detects malware and takes them off but when i restart the computer i go on internet explorer and go to google search tab it starts to redirect to advertising websites like it did before i used malwarebytes is there any other websites that can help me or other programs? and why isnt taking off is malware that bad of a bug to take off?