Please use the AVG Remover utility which can be downloaded here.
Make sure to use either the 32-bit or 64-bit version, depending on your operating system's architecture.
The whole uninstallation process involving the AVG Remover utility is described in details in this AVG Forums article.
everytime i tried to uninstall AVG it was either automatically restart or the screen is freezing/stucked and eventually won't continue to uninstall it.. how could i done this successfully.. pls help! asap.