The setup file will only have the virus database that was in force when it was created or updated and depends on where you downloaded avast from ?
So when installed you should do a manual update as onlysomeone suggests. The avast updates are incremental (unlike many other programs) so the actual download will only get those updates between 080418-0 and the latest update 080510-0.
So right click the avast ‘a’ icon, select Updating, iAVS Update and you should be good to go.
You shouldn’t have to do anything, if the auto update is working you will get a Blue pop-up window in the bottom right of your screen when an update has been done and an audible notification (assuming you have speakers turned on).
Well the Red pop-up indicates the update failed, and the most common cause is a firewall blocking the update process.
What is your firewall ?
Does it allow avast.setup internet access ?
If it does delete the entry for it and do a manual iAVS update, this will force the firewall to ask permission again.
Another possibility is do you use a proxy to connect to the internet, if you do you need to set that proxy info into the program settings update process. We can deal with that later if you do use a proxy ?