and seeing them is really irritating.
It's supposed to be so and tells you that you'r system is not secured enough..
btw: about which messages/shield are we talking here ?
standard shield, net shield, webshield ?
you can't turn off the "virus found" message from standard-shield in avast HOME edition (or are you talking about the continuous messages/which files are scanned ? this is disabled by default: see config to disable it..),
but you can disable them for net shield (and maybe for webshield, not sure about that one..)
please check in the respective configuration of the Shield(s) and also please use the board-search here..