Look at Resident Shield, Properties:

Other options on this tab include:
Scan all files - select this if you want the Resident Shield to check all files, regardless of their extensions or contents. Scanning all files can be more demanding on system resources, which may adversely affect computer performance.
Scan infectable files - select this if you want the Resident Shield to check all potentially infectable files.
Press the Advanced settings button to open the dialog Resident Shield - Advanced Settings. This dialog serves as a summary of what extensions will be scanned by the Resident Shield; options are not available in AVG Free Edition.