First let me point out that this isn't recommended to disable your AVG Free AV nor needed usually anymore, no matter what the software says. We've installed everything from common programs to system drivers without any trouble while still running AVG. The "disable your AV software" is a carry-over from the old days where they would commonly interrupt an install thinking it was suspicious, this has never happened to us once with AVG.

To disable it though.. open the Control Center, double click the Resident Shield and remove the checkmark next to the 'Turn on AVG Resident Shield'. Don't forget to re-activate it when you are done....

With Win Vista.... open the Windows Start Menu.. navigate to the AVG Control Center... right click and select "Run as Administrator"... you may get asked for the admin password if your user account you are preforming it from isn't the admin account and then make the change.