Thanks for tips and link.
One computer up and running now, my son's. Got into the BIOS and checked all enabled or auto. Disk Management was the place though. Recognizing 'foreign' disk from the former XP machine. Great tip.
All looking very nice now, water-cooled and a UV light to make the fluid glow!
Now to attack the neighbour's Vista again.
Not a bootable disk or bootmgr missing.
Still a few ideas needed.