Yep. Did that. It seems as if it's accessing the DVD but still says No OS.
Mint will need to re-do the partition schema, so if it doesnt see any available drive space on your NTFS formatted drive, you may need to tell it delete the old partition and use all available space after that.
If I could get that far I'd be happy. :(
If you have an external DVD drive you may have to choose “USB” in the boot order rather than “DVD”.
When you burnt the ISO for Mint to a DVD, did you copy the file? Or let your burning software burn the image inside the ISO?
If you just have the ISO file on the disk, there’d be nothing there to mount.