Assassins Creed 4 Black Flag – How to Check if Multiplayer is Functional

Try lowering the graphics settings if possible. It's likely you have them set higher than your system is capable of running.

If you have a 64bit OS, the cheapest and immediate performance upgrade you can do would be a simple RAM upgrade. Ram is still relatively cheap these days, and bumping yourself up to 6 or 8GB if possible will yield a nice boost all around, not just in gaming. Modern OS's like Win7 are pretty RAM hungry, and if you are running a game on top of that, it may starve it out causing your OS to Swap/Page RAM onto your hard drive, which is considerably slower in performance. This is likely part of your problem.

Also, a video card upgrade usually is the single most important/cost effective/noticeable upgrade you can do for gaming. It provides immediate and noticeable results. I recommend checking out Tom's Hardware GPU Hierarchy Chart. They update it usually every month and it gives a general idea where your video card stacks up against what is out today. As they recommend, it's usually not worth upgrading until you jump 2 or more levels on the chart. Then you get the best bang-for-your-buck. I tend to upgrade my video card usually once every other year, sometimes every year (depending on my tax refund, hehe). But, I consider this more frequent than most, so every other year or so you can probably get away with and still playing most games on high/medium-high settings, given there are no other bottlenecks such as RAM or really slow hard drives (5400rpm drives).

http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107-7.html

If your specific card is not listed, just round-about-it, such as 6350 round to 6300 series or there-about to guestimate where your out.

The only solution that worked for me was to reinstall Windows 8.1.

After deep investigation, I found that one of the DLLs for DirectX was corrupted.

I tried to update DirectX but it keep informing me that I had the latest version with no errors.