Have you tried an explorer search for avast5.ini whilst it is in this location C:\ProgramData\Alwil Software\Avast\ on my win7 system perhaps it could be in Users on yours.

You could try making a change in the avastUI, Settings that would be reflected in the avast5.ini file which may create it if not present. AvastUI > Settings > Updates > Details and change the Auto-update interval from the default value to something different 123 minutes (as there is no way that interval is a default), that would need to be recorded in the avast5.ini.