How good are free anti-virus programs?

[Greggoman]

My experience with AVG is it is always updating and wants to restart your PC  and does so whenever it feels like it regardless of scheduling times you set up.

mmm i agree. AVG seems to be need an update every time i turn the computer on and so it gets updated 4 or so times a day yet still needs more 

[Newbie_From_Hell]

AVG doesn't "need" to update all the time, it checks with the server alot to try and be as upto date as possible, AVG tend to release definition updates as soon as threats are released, which can potentially be a couple of times a day.

but each of this updates are normally less then 100kb in size (about the same as half page word document).

you can turn off the pop ups alerting you to the updates.