Werner,

1 The DVD drive can read a DVD because I can "see" the Knoppix DVD in the File Manager "PCManFM". In /media/sr0 I can "see" KNOPPIX_V7.4.0DVD-2014-08-01-EN.iso

2 It can not boot up from the DVD drive. Nor the ISO DVD from Knoppix, nor the ISO from the book "Linux for Dummies". This is the problem. The DVDs are visible in the File Manager, so it can read a CD/DVD. It can not boot from the same DVD.

3 I put a windows DVD in the DVD driver. I can "see" it in the File Manager.

Thank you,

hansieb