About the only thing I know of that will help you speed up your Nvidia card is:
Download the 'Coolbits' registry hack. Be sure you've downloaded and installed the latest drivers for your Nvidia card from:
http://www.nvidia.com
Once you've done that, double click the Coolbits file you downloaded, it will ask if you're sure you want to add that information to the registry. Click Yes, then, when it's all done, reboot. (I've put a link to Coolbits below, but read on before you start).
Once you've done that, and have rebooted and are sitting back at your desktop, right click on the desktop, pick Properties, pick the Settings page, and then click the Advanced button. One of the tabbed pages in the advanced section should have the name of your video card on it, pick that page, look in the scroll box on the left, you should see tons of options. Among them, now that you've run the Coolbits registry hack, you should see 'Clock Frequencies'. In there, you can CAREFULLY overclock your card.
(A hint, unless you have a super cooled machine, don't try raising your Core speed more than say 10 or 15. Before you change it, note the number, then divide your vid card's Memory speed by your its core speed. You should come up with a number around 2.3. or so. Once you know that number, set your core speed up say 10 points higher than it was, and multiply the new core speed by the number you got by dividing memory speed by core speed, and you'll know the best number to set your memory speed to).
Fair warning, you can gain a nice boost in performance, but if you turn it up too high, your machine can lock up, or you can get visual 'artifacts' in games, (little graphic glitches), or if you are really too agressive at overclocking it, you could potentially damage your video card. So keep this in mind before you undertake this task!
I have overclocked every Nvidia card I've owned since my original GeForce 256, and never had any problems. But I'm pretty skilled at computers, and I have no less than 5 normal sized cooling fans in my machine, as well as 1 huge fan in the side blowing right down on my video card and CPU.
Again, be sure you're willing to take the risk before you try this. You might search the web to see what settings other overclockers have used on your model card successfully, too.
Here's the link to the Coolbits reg hack, in case you decide to give it a shot:
http://downloads.guru3d.com/download.php?det=201
Good luck, and may fortune favor the bold. ;)