Well, each card is a bit different, so I'm not sure what applies to my FX 5700 would apply to your GF3 because my friend used the program on his GF2 and there were some features mine had that his didn't. I'm going to try and explain it the best I can so bare with me
Aright you should see two menus.... the 2nd one should say DRIVER SETTINGS and will say what kind of drivers you have. Since I downloaded the Forceware drivers from nvidias site, mine says 'Forceware Detected' if you look to the right of where it says what drivers you have you'll see a little arrow pointing SouthEast that says Customize... Click that and it brings up a menu of Icons. You want the very first icon that coincidentally, looks like a graphics card, this when you hover over it says, "System Settings" and this is where the overclocking begins.
You'll have to click "ENABLE Driver-Level hardware overclocking"
Now this is where I'm not sure where the cards differ at. For me I have the options of "Standard 2d", "low end 3D" and, "performance 3D" under the drop down menu to the right of the "ENABLE" button.
BTW: When you click that enable just hit DETECT NOW, you won't need a reboot because you aren't overclocking right now (and if you ARE overclocked right now then you DO want to hit reboot)
After you've done that you should see some sliders to adjust your frequencies..
Now remember where it said Forceware Detected? Right above that is nother menu that also says Customize with an arrow pointing SouthEast, it's directly above the one you clicked to get to these settings. If you click that upper Customize button, then click the 5th icon over that looks like a RAM chip it says HARDWARE MONITORING and it'll tell you your current core and memory speed, and plus then you'll be able to visibly see the OC go up and know what it's at.
I hope this helped some, feel free to post in this thread again with another question if you have one cause I'm a pretty bad teacher
the 2D is when you're simply in windows and you can adjust that quite a bit with no worries, and the performance 3D (assuming you have that in the drop down menu) of course is for the games and whatnot, I have my 2D and 3D settings at the same speed, but that's just me. Then hit TEST SETTINGS, APPLY, and APPLY AT STARTUP if you wish to otherwise it won't save the settings and when you reboot, back to normal they go
You can boot up in Safe Mode if you've overclocked your card too far and you can't boot into windows cause it's so distorted