Windows fails to load.

[#1]

Is the cd a retails version or a OEM. If its a OEM it may be bios locked. The cd maybe scratched try coping it and see if that works.
In the bios there should be an option like load fail safe defaults try that to see if it helps

[#2]

This is a retail CD and do not think is is scratched or damaged.  I did a full installation from it recently on the old HD that is on its way out.
It is not as though the disc does not run at all.  You can see all the major files/progs/drivers etc loading at the bottom of the screen.  Its only when Windows Setup starts that its says "not a valid Windows DC.
Is there a way to move the whole of Windows from the old (troublesome) HD onto the new (virgin) HD?

[#3]

You can use a disk image tool to copy the disk over it may throw a wobbler as its an ide drive but you have more chance than going from ide to sata
For free imaging tools see
http://www.thefreecountry.com/utilities/backupandimage.shtml
Acronis is the best and they were giving a old version away free the other day there is a thread for it on the forums

[#4]

Have made a full back up of the whole of the old HD useing Acronis True Image as advised but when I come to 'restore' onto the new (virgin) HD the new HD is greyed out and not selectable as a target.
The new HD shows up ok on the BIOS and it shows up on Device Manager but its not visible on Explorer.  Any ideas please.

[#5]

You should have put both disk in boot from Acronis cd(you can create one from within the software) and then do a disk copy. Then remove the old drive first and boot from the new drive hopefully dont forget to set it as the boot drive.
If its a new drive it will have no partition so windows wont see it but it should show up in disk manager