I've ran AVG For years and never had an issue (Well but then i know what i'm dong haha) but it has saved a few of my clients because that is what we put on unless they want something else.
If you do go with AVG this will save you some time
http/free.avg.com/us-en/download-free-all-product
Download the x32 or x64 depending on what you are running. These are the full files not the download install. Its nice to have these and hard to find it. Plug the AVG website does everything they can to get you to buy it.
Once you install it do this. Open the AVG UI. Then in the upper right click on Options and then Advanced settings. On this page there is the System Tray Notifications. Uncheck the top one "Display System Tray Notifications". and the rest should grey out. This will get rid of any annoying pop-ups they try to get you to click on.
Also sometimes on a program update they will upgrade you to the "Trial" Version. If you find yourself and other programs unable to connect to games, computers, network printers, AVG is the issue. It install the trial with the firewall (the free version doesn't have this but you are fine with the windows firewall). What you want to do is go to the Control Panel and then go to Programs and Features (Add/Remove programs for XP) and then select AVG and click Uninstall. On one screen it will have some options. One should be "Downgrade" click that let it run and you will be back to normal.
Also out of a lot of AntiVirus programs AVG seems to take up the least amount of resources as well.