Solution

You can uninstall avast! just as any other software - using ADD/REMOVE PROGRAMS in Control Panel. If any problem appears, use the avast! uninstall utility.

The exact way:

1. Click on START button.
2. Select SETTINGS -> CONTROL PANEL (or simply CONTROL PANEL - it depends on your Windows version) -> ADD/REMOVE PROGRAMS.
3. From the list of installed applications select avast! Antivirus and click on CHANGE/REMOVE button.
4. avast! setup starts. Select UNINSTALL and click on NEXT.