If you need to exclude a certain file, folder or URL from any detection by AVG, please follow these steps:
Open the AVG Admin Console
Go to "Options" menu then click on "Advanced Settings"
Click on "Exceptions" on the left hand menu
Click on the "Add exception" button located in lower left hand corner of this window
Choose the Exception type this dialog window
Now find the file or folder you want to exclude and click OK to save these changes

These exceptions can be used for "Potentially unwanted programs" only. If you set the exception for a viral file (Trojan horse, I-Worm, Worm, W32...), this file will be still detected by AVG tests and the AVG Resident Shield.