Avira 10 has now been reported as an ad-supported program including a toolbar that requires you change your search provider to ASK.com. If you do not like advertising popups appearing on your screen, please consider a different free antivirus program. Microsoft Security Essentials is one suggestion as it covers spyware also.
I have been using Shaw Secure for quite a while now and it has worked flawlessly for me so far. There have not been any crashes or major problems with it interfering with the operation of applications unlike some of the other more well known security software bundles.