AVAST 4.8 AND NOW 5.0,

I HAVE THE ABILITY TO USE THE UPDATE OF ONE COMPUTER TO UPDATE OTHER COMPUTERS WITHOUT CONNECTING THEM TO THE INTERNET

Welcome to forum

To Update from 4.8 to 5.0 just download new setup from http://www.avast.com/download-software#tab2 depending on your license (Free, Pro or upgrade to Internet Security).

To update virus-database download update from: http://www.avast.com/download-update

Download the update here: http://www.avast.com/download-update

Or copy 400.vps file from an updated avast installation to a USB stick and transfer it to the \Data folder of the off-line computer (having disabled the avast self-defence module first).