Hello, I have solved the problem but I don't know why it now works. If I boot the 7.3 USB Key, go to troubleshoot then select installation with basic graphics it all works. I can then boot the system disk and set up the full graphics. As an experiment I tried both 7.2 and 7.4. The above rules apply to 7.2. With 7.4 it works with no problems. To tidy up the boot process 'irqpoll' needs to be included in the boot command line/grub. Thank you for all your suggestions. Mark -- This email has been checked for viruses by AVG. https://www.avg.com