1. Assuming that you installed avast! in the default folder, this is the path needed to scan downloads, C:\Program Files\Alwil Software\Avast4\ashQuick.exe

  2. These advanced automated options are only available in the Pro version.
    Check this work around out - HOWTO: Scheduled Automatic Scans avast! Home Version!

The major disadvantage with the task scheduler trick of using ashquick.exe is, it will scan every file of the hdd, partition, folder or file that you set it to scan; even those files not considered a potential threat, this can take a long time. It is possible to add certain folders to the exclusions list for say your media files, etc. This could leave you vulnerable if that folder got infected as it wouldn’t be scanned by the on-demand scanner as you have excluded it.
The Pro version gives a lot more flexibility and the scan would follow the settings and exclusions, etc. of the regular scan.
With the different levels of protection of and the fall back of the Standard Shield, I find the need for daily scheduled scans lessened. I prefer to do a manual scan with my regular weekly maintenance tasks.

  1. There aren’t that many firewalls that are Vista compatible, then again you don’t say if you are prepared to pay, as there are I believe fewer free firewalls (worth a look), I believe Comodo and PC Tools Firewall Plus are either Vista compatible or close to release. Don’t know much on Vista compatibility as I’m not using it.