Please do this:Click the link at the line following File > Preferences > More preferences can be edited directly in the file.Delete the "staging" subfolder of the folder that opened when you clicked that link.Try installing Arduino SAMD Boards again.
I saw a similar CRC error while trying to install SAMD support. Cleaning the staging folder didn't help. The Arduino Boards Manager attempted to download "http://downloads.arduino.cc/tools/arduinoOTA-1.2.0-windows_386.zip" but our company firewall modified the ZIP file to say "Gateway Anti-Virus Alert. This request is blocked by the Firewall Gateway Anti-Virus Service. Name: Downloader.A_1901 (Trojan) blocked."