Anyway I think you need a faster CPU and Graphics card to run Assassin's Creed smoothly and on high settings. The 9500GT is considered pretty old now, I recommend getting HD5770 to run high settings without much lag; it's a cheap buy, and a faster CPU would help a lot I believe. However, this all really depends on what resolution you actually play on.
RAM is fine I think but another Gig or two wouldn't hurt, in fact it would help a lot
If you can afford these upgrades you can play most games on high settings.
Even though your card has 1 Gig dedicated RAM, its only a 128 bit card, which is lower than recommended for the game, unless you run the game no better than 1024 x 786, with low graphical quality.
when games recommend specs, they actually refer to the bit rate of the card (or should) , the 8800GT is a better card than the 9500GT (Remember, the higher the model number doesn't mean the card is better)
8800GT boasts a 512mb dedicated RAM and a 256 bit rateand was a great card in its time, try upgrading to a card with a 256bit rate or better, the GTX 260 has a 448 bit rate and is a good deal!!
all of my recommendations are aimed at higher graphical transfers! now to a better communication transfer between your card and CPU:
you're probably running an Intel E6400 @ 2.13 Ghz?? the game recommends 1.8 Ghz Core 2 duo, and your CPu only hosts a 2M Cache, maybe a slight overclock to 2.4 or 2.5 Ghz (remember, every little bit counts!), or upgrade