It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

czarevilsam: Attempting to start the game as "Diablo" (not "Diablo (Classic)") results in an error where it requires the CD in the drive. Pressing "OK" loops back to the same error, and pressing "Cancel" brings up an issue that it is unable to load the file "diabdat.mpq".

Running a repair and running as administrator had no effect.
Did you have a previously installed Diablo on your system? This might be what causes this issue.
it's possibly registry related, either the installation got messed up or the AV did.

I would suggest submitting a ticket to our Technical Support :
Thanks guys for submitting the tickets, we'll look into this.
high rated
That error suggests something went wrong during installation and one of registry keys is either not set or not read properly.
As a quick workaround, try copying diabdat.mpq from root folder to DX folder.

The key in question:
HKLM\SOFTWARE\Wow6432Node*\Blizzard Entertainment\Archives\DiabloCD
should point to the game installation folder.

*on x64 machines
Post edited March 07, 2019 by Thiev