NBRT does not work at all. I've downloaded latest files to USB, and when I start PC it boots to USB fine but fails to scan. I also downloaded an .ISO file, burned a DVD and started it in PC. It would not load at all. I have a MEMTEST CD that boots just fine so it is not a boot issue. Getting fed up with this issue. Have tried it on same PC as Norton is loaded on, and two others that have no AV at all. (Recently got rid of free AV programs) All with same results. It boots up fine and does a virus definition check/update which takes, but then it does not perform scan. It states "Scan failed" with no explanation as to why. Update 1/24/18: I've just formatted the USB drive and downloaded the latest .ISO image and placed it on the USB drive. Now I get a "disk error" message with no boot at all. So I have effectively killed the NBRT at least booting into a workable environment into a "nothing at all" scenario. I am getting really fed up with Norton's BS and am seriously thinking of cancelling my subscription after being a loyal customer for the last eight years.
cdr100560 Follow this guide to use the NBRT iso. It sounds to me as though the image you have has not been made "bootable" and/or your BIOS isn't allowing boot from that media type. Did you download the boot image creation tool "Rufus"?
https://support.norton.com/sp/en/us/home/current/solutions/v72380755_EndUserProfile_en_us
Cheers