Pondus
4
you have removed any previous installed AV ?
and used a removal tool to clean all leftovers http://uninstallers.blogspot.com/
Then try a new clean install
remove avast with this http://www.avast.com/en-no/uninstall-utility
Run CCleaner and reboot http://www.piriform.com/ (remember to untic the toolbar installer)
Run Eusing free and reboot http://www.eusing.com/free_registry_cleaner/registry_cleaner.htm
Install avast and reboot