Firstly, please make sure that your PC meets the The Witcher 2: Assassins of Kings system requirements
If the requirements are met please try the solutions below:
1. Reinstall your GPU drivers. To do so completely follow these steps:
2. Uninstall all of the Microsoft Visual C++ redistributables that you have installed.
Once it's done install the Microsoft Visual C++ redistributable packages from the link below starting from the oldest ones (skip the "arm" files). Launch all the executables as Administrator.
https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads
3. Disable all unneccessary apps before launching the game (especially apps with overlay) such as:
4. Please try launching The Witcher 2 in a clean boot mode. Here is how to perform clean boot - https://support.microsoft.com/en-us/kb/929135/
If none of the above will help, please report the issue to us, if there is any information or error code displayed please make sure to include it in the description.