Can't access backup, Windows Security is asking me for credentials
I did a full disk backup of a PC using ATI 2019 (booted from CD) that isn't booting into Windows 10 v20H2 anymore - I am getting 0xC000021A error after a system restore. In Windows recovery environment I can see my data files are still intact. I did the backup with intention of clean install following by restore of my data files.
Before doing clean install I wanted to ensure I could access my data files in backup. So, I go to another PC in house that also has ATI 2019 installed and try to access the backup. First of all, when I right click on the backup the mount option doesn't show up. When I try to open the file to browse it a Windows security window pops up asking me for credentials. Nothing I try lets me access the backup. I use the user name and just blank entry for password since that account has no password - doesn't work. I've also tried Administrator with the password (other account) and that doesn't work either.
Any ideas on how to access this backup file? I'm not going to do clean install on the non-booting PC until I am 100% certain I have ability to restore data files.