Your graphics card isn't up to the task. The 9500GT is a really weak video card by today's standards. Try turning your graphical settings down to as low as they can go, that should improve performance a bit. If that doesn't get you smooth gameplay, look at getting a new video card. Also check how much RAM you are using while playing using task manager. Witcher 2 can use a lot of RAM, and you might be going over 3GB also causing bad performance.