You can use AVG Remover. Download and install the 32-bit or the 64-bit version from the AVG Technologies download page. Also you can try using Revo Uninstaller. Even if it can't uninstall the application normally, it will force it to uninstall by wiping out all traces of its presence from the system.
After that, try running AdwCleaner to make sure that there are no leftover rogue registry keys or toolbars in your system.
