Spent the day 'repairing' the computer again. I think I finally found out what the problem is/was. Turns out when you put this new video card in the computer it for some reason changes the order of the boot devices in the bios. It's a simple change to change the order of the boot disks. Haven't got a clue why it does this, but it's very reproducible. Unfortunately I have already formatted my main drive and now will spend the next 2+ days rebuilding the 'catalog' to try to restore the system. Have installed Win2K3, 'temporarily'.
Stayed up way to late [mid-night] to win an EBay auction.