Liz,
I will be glad to help you if you can give me the answers to the following:

When I take avast off the start up menu, the blue icon ball disappears off the system tray.
Please explain what you mean by the Startup menu? Do you mean the Start in the lower left corner of the tray? or are you referring tot the Start Program folder in Windows? I do not understand.
I have the icon on my desktop, and i can get to the menu, but, silly newbie that I am ::)I can't figure out how to make avast start doing it's regular 'background' scanning
If you click on the desktop icon, what exactly appears: the On line Protection screen or the Avast scanner interface?

Where exactly do you see this “Disabled” message?

Thanks,
techie101