What do u think about this proccessor?

This build is considered to be rather outdated. The E8400 was a good processor 2 years ago but now it's nothing. I'm surprised that still find them. I would recommend building a new computer for gaming say i5-2500k and gtx 460 with 4gb of ram. Even if you upgrade your cpu the game performance of assassins creed will not significantly improve because it is more about video card when it comes to gaming. If you're unable to play it right now the same will happen even if u get the e8400.