I recently installed the Witcher 2 and I could not get it to start past the game launcher. It would just hang on the wolf emblem. Searched for various solutions and I couldn't find anything that would fix it. Eventually I found a steam topic that suggested to limit the cores that Witcher 2 uses. I have an amd 3950x. Anyway I opened the launcher, while in the launcher I went to the task manager and then went to the details tab. Found the process and set the affinity for 4 cores. Launched right away. Hope this helps someone else with a high core cpu from amd.

Whoops I meant to put this in the Witcher 2 forum. Maybe a moderator can move it.

Same cpu, same problem, same solution.
Thx, begolf00