Generally speaking, yes you should have a 3ed party antivirus on top of the Windows built in software. In this particular case I would check the startup items to see what's apps are loading in the background at startup. To check click the Windows button and click run. Type in msconfig and click enter. Go into the startup tab and take a look. Be very carful not to turn off any Windows and PC component processes or you might run into problems with your computer bootup. If you're not sure what the service/app does you can Google the name and read who created it and whether you need it. If you make any changes you'll need to reboot. Hope this helps.