[Trisquel-users] Live DVD Trisquel 8.0 64bits issue

[anatom]

Hello everybody,
the Trisquel 8.0 64bits Live DVD does not work. Grub starts, but when I  
choose the "Run Trisquel without install option", nothing happens except that  
I can hear a lot of noise from the DVD drive. The same for the "Checking the  
disc for damage"-option. Even waiting for a couple of minutes (until I've  
finished doing my dishes which takes a while) did not bring anything but a  
black screen. The screen is lit, but it is completely black.
It has been suggested  
(https://trisquel.info/en/wiki/installation-troubleshooting) to press F6  
without saying when to press it. I hit F6 when the GRUB option menus turned  
up, but it didn't have any effect at all.
I need a backup system before changing partition size -- in order to upgrade  
to Trisquel 8. So, I'd be happy about any help.
Thanks in advance for any advice.