How much RAM do you have? If system is that old it may need Lubuntu not full Ubuntu as that needs a good video system.
You need the older 173.xx series nVidia driver.
Lubuntu, which uses the LXDE desktop environment, targeted at "normal computers" with 128 MB
With 512Mb of RAM and almost any processor, Lubuntu will perform more than adequately out-of-the box.
I'd suggest to check amjjawad's thread (Lubuntu One Stop Thread) and you'll find many useful information.