I don’t know what’s advised in general about what to use or not. I personally only use the 3 shields and the software updater.

You really need to test it in your own environment to know for sure how it’s going to work for you. The installer is easy enough to run (pay attention to all the checkboxes).

Free version : http://files.avast.com/iavs9x/avast_free_antivirus_setup.exe
Pro version : http://files.avast.com/iavs9x/avast_pro_antivirus_setup.exe
Internet Security version : http://files.avast.com/iavs9x/avast_internet_security_setup.exe
Premier version : http://files.avast.com/iavs9x/avast_premier_antivirus_setup.exe

Plus Avast provides a tool that will completely remove it if you choose not to keep it:

AvastClear : http://files.avast.com/iavs9x/avastclear.exe

-Noel