(Question + answer since it took me 12 hours to find a solution)
I had big trouble installing Windows 7 (Professional or Enterprise) on a Samsung NP900X3A, without using the recovery media DVD or after the harddisk / SSD has been completely formatted.
When installing from a bootable USB flash drive / stick, I got the following error messages:
Required cd/dvd drive device driver is missing.
And later on:
No new devices could be found. Make sure the driver files are correct and located on the driver installation media.
For me the trick was to remove the USB flash drive from the left-side port after getting the second stated error message. Then click the window close button and go back to the installation start screen. Stick in the same USB flash driver into the right-side port and click "Install now". Installation now continues flawlessly.
No additional drivers needed, just switching ports does the trick.