Geforce 3, but games aren't smooth!

[OK]

System Info:

OS: Win ME
Processor : AMD 1333 T-bird
RAM: 256 MB
Hard disk type: IDE
Hard disk model: 61 Gb 7200 RPM (IBM)
Motherboard: Asus A7V-133
Graphic card: MSI Geforce 3 Ti 200, drivers 2183
Sound card: Soundblaster 128
Video capture card: Pinnacle Studio PCTV Series (RAVE, PCI)
Other cards: Firewire card, 10mbit network card

Problem:

I can't play games with smooth graphics. The FPS seems to be OK,
but about once every 1-2 seconds there is some kind of delay/lag that destroys the gaming experience. It's not due to "loading in the textures", because its not only at the beginning of the gameplaying session.

For instance, Sacrifice, which came with the Geforce. When I run forward, the movement of the ground is not smooth due to these small "jumps". I thought it could be a program running in the background but I closed all of those. I've also had similar problems with other games.

This annoys me. What is the point of having a Geforce 3 when I can't play with smooth graphics anyway?

Anyone know what this could be? Any help would be greatly appreciated.