One could not even get to the BIOS to change the boot.
It finally it has now been solved
It took multiple calls to the DEll offshore support (the one with the heavy accents difficult to understand). They always go for the simple over and over stuff (pull the plug, strip out the memory, etc. etc.). When it of course still doesn't solve the problems, and they run out of ideas you get mysteriously disconnected.
Eventually after taking names you finally get somebody on the phone who gives up on the stuff about the user screwing it up and offer to replace the motherboard (it was only 2 months old out of their shop).
Motherboard replaced and it works fine!