I recently installed Witcher 2 on Windows 10 (Version 2004) with an AMD Ryzen 9 3950X (16 Cores/32 Threads).

The launcher starts fine but launching the game from the launcher fails:
Only the wolf logo splash screen shows and nothing happened no matter how long I waited. (No crash or error message)
The Task Manager showed "witcher2.exe" running in the background with RAM usage frozen around 200MB.

I spent several hours trying to fix this and only after a long while I found in a forum somewhere in a burried comment some hint and so I decided to post this solution so it could be more easily found.

The issue seems to be with my CPU having too many cores/threads available since I played it a few years ago with exactly the same system except that I upgraded my CPU earlier this year.

The solution to my problem was that I had to manually set the Processor Affinity of the "witcher2.exe" and the game started just fine. In my case I set the game to run on my first 16 cores/threads but I don't think it matters how many or which cores you assign it to as long as the affinity isn't set to the default "All Processors"setting.

One thing to take note of is that affinity can only be set on running processes and Witcher 2 will crash if you change its affinity while it's running. To circumvent it you'll have to start the game (witcher2.exe) or its launcher via a CMD command to set the affinity at startup:
start "" /affinity 0xFFFF "<Path to game folder>\Launcher.exe

0xFFFF is the hexadecimal bitmask which indicates which cores to run at. in my case its the first 16. There are some processor affinity calculators online which will give you a mask for your settings.

In my case I wanted to play Witcher 2 with the GOG Galaxy Client so starting the game from CMD wasn't an option. Processor affinity is inherited from the parent process.
So in my case I created a desktop shortcut to the GOG Galaxy Client which launches the GOG client from CMD and sets its affinity so when I start Witcher 2 with GOG it'll have all the GOG features (achievements, playtime etc) and the startup fix applied:
C:\Windows\System32\cmd.exe /c start "" /affinity 0xFFFF "C:\Program Files (x86)\GOG Galaxy\GalaxyClient.exe"

I hope this post might help some people who run into the exact same problem. :)

Dude, you're a genius, i don't even know how did you go this far to find that solution, but it really helps me out.
By the way, I have the same kind of Cpu (Amd Threadripper 1990X) hence the same kind of issue.

YOU'RE A GOD. THANK YOU

Thank you for this, this also worked for steam.
C:\Windows\System32\cmd.exe /c start "" /affinity 0xFFFF "C:\Games\Steam\steam.exe"

Same issue. Solution worked perfectly. Thanks!
Slight variation on solution - you can just modify the target of the shortcut created by the installer (you might need to modify the path, but mine is installed at the default location) to -
C:\Windows\System32\cmd.exe /c start "" /affinity 0xFFFF "C:\GOG Games\The Witcher 2\Launcher.exe"

Hello !
I have the same problem but the fix with the processor affinity is a little bit complicated for me.
Can you help me plz, I have a i9-13900KF.

Edit:! I found another way to fix the problem but your post allowed me to know about the problem with the processor so thanks anyway !

Can you share this other way? I have the same processor as you

Oh sorry I thought I would get an email if someone answered to my post.
It's very easy just replicate what the guy does in this video (Don't pay attention to the part about the keyboard): https://www.youtube.com/watch?v=QVSuaQiQj3w
For me it works perfectly now.

I am playing the Steam version, but this solved my problem on a new 13900KF CPU.

If you can't watch the video, or it is removed, the solution:
Open the Witcher 2 Launcher
set the affinity for Launcher.exe in Task Manager to only use one CPU (can by any of them)
Select 'Launch game' from the Witcher 2 launcher and you will see the wolf logo indefinitely
Again go to task manager and set the launch affinity for witcher2.exe to use all CPU's (or more than just 1, at least).
If this worked, after a couple of seconds the game should launch with your desired graphics settings.

If all else fails, try performing a clean boot of your system to eliminate any potential conflicts from other running programs. This will determine if any background processes are causing the issue.

THANK YOU SO MUCH!
I have spend 3 days trying to solve the problem...
I have an AMD Ryzen 9 7950x3d... Now works perfect...

THANK

Wow. I never received any Emails about replies to my thread. I just came across it after 3 years and I'm really happy that this post helped that many people!

There is no need to complicate your life with commands, just go to system settings (MSconfig) -> Boot -> Advanced Options -> And set the number of cores to a lower one, in my case I have a 32 core i9-13900k, I set it to 16 and the game works perfectly.

Please OP, if you read this, mark this post as the thread solution. It's the quickest and easiest, no need to complicate your life with commands or strange launch parameters.

This is not an ideal solution, as you're effectively disabling several cores system wide just to play a single game, and would need to change the setting back and reboot if you want all your cores back.

Thank you for this solution. It works great. I really wish CDPR would update/fix their game though.