Why can i run Assassin's Creed 3 but not Assassin's Creed 4?

[690]

Why does Assassin's creed 3 run smooth for me but i can't run Assassin's creed 4 without enormous lag?Can anyone please help me with this, my specs are:
MS Windows 7 Ultimate 32-bit SP1
Intel Core2Duo CPU E4500 @ 2.20GHz
2,0 GB RAM
NVIDIA Geeforce 9400 GT
Assassin's creed 3 runs like butter, i only experienced a few fps drops in my entire gaming time, and they lasted for about 5 seconds. All settings were on normal with Vsync and Anisotropic filtering off, it looked beautiful and i enjoyed it fully.
On the other hand, i installed Assassin's Creed 4 Black flag and i cant even make it run without horrendous lag with EVERYTHING possible to the lowest and off, even with the resolution changed too 800 x 600.
I tried messing with the NVIDIA console based on some tips from the internet but the horrible slowness wont go away, i dont understand why this is, the requirements are the same for AC 3...
Does anyone have an idea?

[Barry Manilow]

Good god your computer is awful. There's no wonder it won't run. No the requirements aren't the same.

Minimum System Requirements

Operating System: Windows Vista SP2 or Windows 7 SP1 or Windows 8 (both 32/64bit versions)
Processor: Intel Core2Quad Q8400 @ 2.6 GHz or AMD Athlon II X4 620 @ 2.6 GHz
RAM: 2 GB (4 GB recommended)
Video Card: Nvidia Geforce GTX 260 or AMD Radeon HD 4870 (512MB VRAM with shader Model 4.0 or higher)
DirectX 11: DirectX June 2010 Redistributable
Disk Space: 30 GB available space
Sound Card: DirectX Compatible Sound Card with latest drivers
Peripherals: Windows-Compatible keyboard and mouse required, optional controller (Xbox 360 Controller for Windows recommended)
Multiplayer: 256 Kbps or faster broadband connection

You have an OLD dual core. Second GTX 260 or better. The 9400 GT is also very OLD and neither meet the system requirements