Barry, Try removing AVG by downloading & using the 32 or 64bit 2015 Remover (http://www.avg.com/ww-en/utilities) [Scroll Down], whichever suits your system. If you're not sure about 32 or 64bit on your system have a look @ this link (http://forums.avg.com/ww-en/avg-free-forum?sec=thread&act=show&id=140471#post_140471).
AVG Guru
Suddenly got a message after reboot that my License Key on AVG 2013 was invalid. Re-entered but no accepted. AVG laods in system tray but closes when you try and open. Tried Reset Access and Remover without success. Cannot even uninstall via Control Panel, and even downloading AVG 2015 to overwrite the old software was prevented. Am totally stymied. Any ideas, guys?
Barry, Try removing AVG by downloading & using the 32 or 64bit 2015 Remover (http://www.avg.com/ww-en/utilities) [Scroll Down], whichever suits your system. If you're not sure about 32 or 64bit on your system have a look @ this link (http://forums.avg.com/ww-en/avg-free-forum?sec=thread&act=show&id=140471#post_140471).
AVG Guru