I had the same problem, followed all the advice, could not un-install from add remove so down loaded the avast removal tool and un-installed in safe mode. Down loaded latest AIS tried to install, but kept on crashing the installer. 3 times. So have gone back to last version os AIS 6.0, no problems, will keep this version ansd wait a while....the forums seem to be full user problems, seems the last beta caused all this mayhem!