Thanks for your response.
I have no idea what that (sha256 checksum) is but Express burn said the disc was verified after burning. Used 2 brand new DVD-R verbatim discs. Burned at the only speed I think was offered.
A "checksum" or "hash" is a calculation made from the file(s) in question. Each checksum is unique to the file or files being checked. If anything changes to the file being checked then the subsequent checksum would be different. If the checksum does not match the 'published' checksum then the file is of 'questionable' integrity. Sometimes bits go astray when downloading large files. Sometimes they are 'important' bits!
There are whole web sites and forums dedicated to the discussion of optical media (DVD's/CD's) and which ones work well and which do not. We'll assume you have good, quality discs and that is not the cause of the issue (although I have read that "+R" often works better that "-R").
Although I have not used "Express Burn" I would be surprised if the program did offer an option to choose a "burning speed". I'm not sure how important the actual burning speed is - but after 15 years of running Linux and making literally hundreds of DVD's I can state unequivocally that every Linux site and forum I read always recommended the slowest speed possible (usually 4x although my discs wont burn that slow). YMMV
One other thing I was going to mention in my previous post but did not: I wonder if the process of burning the .iso file
from the USB
though the PC bus
to the DVD may be causing an issue? ( <-- you can see why I did not mention it before ¯\_(ツ)_/¯ )
To calculate the file "hash" from within Windows I believe you can use Windows Power Shell
https://docs.microsoft.com/en-us/po...rshell.utility/get-filehash?view=powershell-7 or download, install and use the "Microsoft File Checksum Integrity Verifier"
https://www.microsoft.com/en-us/download/details.aspx?id=11533
On Windows I used to use "HashCalc" and liked it very much;
https://www.slavasoft.com/hashcalc/
In Linux the "hash" or "checksum" can be generated from the Terminal. Very easy to do.
From the Linux Mint downloads page:
Integrity and authenticity checks:
Once you have downloaded an image, please verify its integrity and authenticity.
Anyone can produce fake ISO images, it is your responsibility to check you are downloading the official ones.
Please read and follow the steps at
https://linuxmint.com/verify.php
Link to the sums:
sha256sum.txt
Link to the signed sums:
sha256sum.txt.gpg
[The above applies to pretty much
all Linux .iso's unless you use a Torrent app for downloading (which checks file integrity and hashes as it downloads)]