zheke16'
I used to use McAfee as it was provided to me for free by my ISP. I bought a laptop so I could take it with me, but McAfee wouldn't update away from home on another ISP, so I tried the big three freebies. It's of no surprise that I settled on avast!. It always updated everywhere I connected to the internet as did Avira & AVG, but avast! will sometimes do it multiple times, the others only once a day. ALWIL will get needed detections to us when we need them without limits.
The ISP I'm currently using also offers the complete McAfee Security Suite for free. http://www.cox.com/ocpv/highspeedinternet/security.asp
I'm staying with avast!, WinPatrol & ZoneAlarm!!! Online Armor.
Do what you feel is best for you.