Whether or not you have the paid or free version of AVG antivirus its latest update will stop your computer from starting. If you able to read this good. Immediately, go to add remove programs in Control Panel, and remove any and all AVG products. If AVG is able to do it latest update there is a good chance it will disable your entire computer. Do not take the chance, remove it. A much better alternative once you have removed AVG is to download Microsoft security essentials. In my opinion it is a much better program.
Without going into great detail at this point. All of these antivirus programs are total bullshit. The most important thing you can do is to keep your computer updated with the latest Microsoft updates. Same thing if you’re using any Apple products, and yes they are every bit as vulnerable.