If you are at HOME with a NON-COMMERCIAL use of your system, you can use avast! Home for free. You can try the Profesional version. You don’t need to download all the setup file.
Go to Control Panel > Add/Remove > avast! antivirus
Choose ‘Change’ action and then check the 2 itens of the Professional version.
You will use a DEMO key untill the 60 days finished. After that you can write your HOME key and use avast! Home. 8)