No Technical, he didn't try it... he said he doesn't have avast! blue icon in the system tray.
aa26668 - have you tried simplest solution ever ?
Right click your START button (Windows) Go to PROPERTIES. Choose TASKBAR tab, and clear the checkmark on HIDE INACTIVE ICONS at the bottom of that window. Now, your avast! blue-ball-icon should reappear in the system tray (close to the system clock). If that doesn't help, then try Eddy's advice... uninstall avast! and then reinstall it from the scratch.
Cheers !