If you haven't already tried to uninstall AVG Anti Virus, you should first try using AVG's uninstaller. The uninstaller should fully remove AVG for most users.
Open the Control Panel by clicking "Start" and "Control Panel" and click "Uninstall a Program" in the Control Panel window. On older versions of Windows, click "Start," "Control Panel" and "Add/Remove Programs." Run the AVG uninstaller by clicking "AVG" in the list and clicking "Uninstall" on the Toolbar."
If you're not reinstalling AVG, click the "Remove User Settings" and "Including Items in the Virus Vault" checkboxes in the AVG uninstaller window and click "Yes." Close any running programs you're prompted to close, such as Internet Explorer, then click "Next." After AVG is finished uninstalling, restart your computer by clicking "OK."

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The AVG uninstall survey appears after your computer restarts. You can provide feedback to AVG on why you chose to uninstall AVG Anti Virus if you choose.