Update, I used Ubuntu's recommended ISO burner, InfraRecorder, it burnt the ISO fine. So I loaded (it even kept my old XP installation as dual boot) and re-booted.
A dos (linux) prompt. Hmmmm. Search the forums on how to get a gui. Followed the instructions, 45 minutes of screen scrolling and updating then re-boot and........a dos prompt.
Repeated this excersize with peoples idea, nothing worked.
So I downloaded the desktop version. I used the same Ubuntu ISO burner and wasted 3 disks. So I used my old Power ISO burner, this worked.
Now I've loaded Ubuntu Desktop, 8.04, 64 bit version. At frigging last
I went to the Dnet site and downloaded the AMD64/ELF Linux version. When I double click on dnet.exe, nothing happens.
Oh well. I've booted it back to XP and it's happily crunching dnet.
Moral of the story, M$ maybe shite and expensive but it works.