To the OP,
Yes, Avast Free is outstanding and I have used it for the past six years. The only critique I have is that some newbies might be put off by the license key registration after the program is installed. If Avast ever releases a totally automated registration system, I think it would be flawless! (An idea for version 7, Vlk, or any of the other techs?!!!) Hehehehe.
The only other AV that I would sort of trust if I had someone who was a know-nothing about computer security would be MSE, because it does not require a license key after being installed to renew each year, BUT the downsides of MSE are:
1.) If only updates once every 24 hours. Avast updates almost always 2-3 times a day in 12-hour cycles.
2.) Avast has Sandox Technology, MSE doesn't.
3.) Avast has Boot Time Scan, MSE doesn't
4.) MSE takes forever to do a full scan, as in overnight. Avast can do it in about about 20-45 minutes, depending on the size of your hard drive and what is found.
5.) MSE just seems a little "too light" for users who may want more protection.
All the other competition AVG, McAfee, Symantic (Norton) just use up too much memory and speed. Avast has the best and easiest to understand GUI around. MSE doesn't seem to have enough there.
To the OP. Why does you father not trust Avast?