Azrael360: When going back to this old game, I found an issue not described here. It affects computers with AMD video cards using the graphics drivers v17.12 (Adrenalin Edition v17.12.1 & v17.12.2 from December 2017). There's a bug in those drivers affecting a few DX9 games, and especially, The Witcher. The problem happens when starting the game, this will crash immediately and only a black screen is seen for a brief moment. This bug was later fixed in the graphics drivers v18.1.1 (bug listed in the 18.1.1 Release Notes under "Resolved Issues").
I found two ways to fix this problem:
#1: The obvious one is to update the graphics drivers to v18.1.1 or newer.
#2: Alternatively, if for whatever reason is necessary to be using the v17.12 drivers and don't want to update yet, using the driver file "atiumdag.dll" from a previous version in the "system" folder of the game also works. For testing purposes, it worked for me using that DLL file from the v17.11.1 graphics drivers. Using 7-Zip, I extracted from the drivers installer the file "atiumdag.dl_", and using 7-Zip again, I extracted from that file the uncompressed "atiumdag.dll" file that later was moved into the folder "..\The Witcher Enhanced Edition Directors Cut\System" where the "witcher.exe" file is. Current and older display drivers installers can be downloaded from the AMD website.
Thanks Azrael, this worked like a charm :) I had to upgrade from adrenalin 17.2.2 to adrenalin 18.7.1 and now can load and play the game without crashes.