Ok. So I don't know what is up, but we download the free trial version of your Avast for Macs and ran it. Everything seemed fine at first, however the next morning we noticed that everything on the desktop was gone and we could not use Finder. After rebooting, Avast automatically came up (along with Mail), but once again, no Desktop and no Finder. We have tried everything to fix this problem, but are now in the process of wiping the computer and re-installing software. You may be thinking, "Why didn't they just uninstall?". Because we couldn't. We couldn't open Finder, and even after finding the Avast program we were not allowed to throw anything away or open Trash. I have no clue what happened, but I just wanted to warn everyone.
Have a happy day!