Right. Seems you cant just "reinstall dx10". Well, maybe you can in some awkward way. So I reinstalled vista, then updated Dx10.
I installed the latest nvidia drivers for my 9800gx2, installed a game "LFS", started playing it for a while. Then it crashed, and now with any driver installed I can not see anything past the window loading bar. In other words, as soon as the windows loading bar is finished the screen goes blank.
Only way to rectify it is to boot to safe mode, and uninstall the graphics drivers and just use the stock drivers.
Anybody got any ideas on this?