Thanks. I have checked with NiBiTor and the 780GTXS should do its job.
At the moment i am trying to do a blind flash.
Have eveything disconnected (HD, DVD) and try to boot from a USB stick.
http://www.notebookforums.com/thread181387.html
This was a very interesting thead.
My blue XPS lights are all on (so it should be posting) but no num-lock-led and no boot from the usb-media.
Think i will give him a few hours of time....
PS I have reseted the XPS Bios. Hopefully it is at standard setting and trying to boot....