How did you install Windows x64 Edition? Was it a clean install, or an upgrade from a different OS?
If an upgrade, did you have avast installed in the old OS? If so, you’ll need to reinstall avast in the new (64-bit) OS as it uses different components as the 32-bit version.
OK, in this case, please open Control Panel → Administrative Tools → Services, and check the status of the “avast antivirus” service. Is it running? If not, can you start it? If not, what error message do you get?
avast service is set to start automatically…but it won’t.
Attempting a manual start gives me the message "Could not start the avast antivirus service on local computer. " Error is 1068-the dependency service or group failed to start.
The avast AVS4 Control Service is started automatically.