AVG had this to say:
To completely uninstall the AVG application from your computer, please follow these steps:
On the taskbar, click Start -> Programs (All Programs) -> AVG 2011 -> Uninstall AVG.
Follow the uninstallation wizard to uninstall AVG from your computer.
If you experience any difficulties uninstalling AVG, please follow the steps below:
Download the latest AVG installation file from the Download section of our website.
When prompted, save the file to the Desktop.
Restart your computer.
Double-click the downloaded AVG installation file on your Desktop.
Click the Uninstall Product option in the Select Setup Type dialog.
Complete the uninstallation process, and then restart your computer.
In case the uninstallation was not successful, please download the AVG Remover tool from following section to your Desktop (tool is available for both 32-bit and 64-bit operating systems). Run the downloaded tool and follow the instructions displayed on your screen.