The aswClear.exe has uninstall for all versions, avast4, avast5, avast6 and avast7, they can be selected from the drop down list.
When I had a problem with Avast 7, I know that I had previous number versions on the system, so I just went through and uninstalled all of them. The uninstall utility found fragments from Avast 4-6, because in past years, I always just used the GUI updater. Since doing BOTH Add/Remove Programs to get Avast 7 out, AND removing all Avast versions, using the Avast uninstall utility, I got a new download of Avast 7, and it now works fine.
On Windows XP I had to enter Safe Mode as an Owner, rather than Administrator, because selecting Administrator did not show the Avast Uninstall utility on the Desktop.
Jack