Browsers won't open and crashing

I may have malware or virus on my computer. I have Norton antivirus on my computer but it seems to be doing nothing . For a week or more,the computer freezes often. now most browsers, IE,firefox, Google either refuse to open or stop working. I keep getting messages that google is crashing. What can I do to fix this problem? Is it something I can do myself or what can I do? Any help appreciated.