Key points
General information
There are two patches available for download on the official page:
http://witcher.wikia.com/wiki/Intro_mod
There is originally no way to walk (as opposed to run) in the OTS (over the shoulder) camera view. A small mod addressing this is available here. The archive it comes in contains installation instructions.
witcher.exe
-dontforceminreqs
<path-to-game>\Data\Override
Override
regedit
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\DirectDraw
EmulationOnly
Sometimes, if you skip the intro cinematic, the mouse is gone on the main menu. This can be fixed by pressing the key that releases the mouse in OTS view(shift by default)
If the game is frequently crashing back to the desktop, running in windowed mode should solve this. A program such as Borderless Gaming will enable you to still run the game in full screen while in this mode.
<path-to-game>\system\witcher.exe