Did you uninstall the previews drivers first?

Try to do these steps:

1) Uninstall all NVIDIA drivers ( mainly in the Add/Remove program)
2) After rebooting you will get a very low visual look, low colors, low resolution but don't mass with the settings just install the ORIGINAL drivers that were given to you when you bought the card (a CD within the box)
3) After rebooting again install [http://www.nzone.com/object/nzone_downloads_winxp_2k_67.02.html]these[/url] drivers (not yet WHQL certified), skip the WHQL.
4) After rebooting the system for the last time adjust the display settings and run some 3d application to test the drivers.

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AquaMark3 score: 25,495 cpu :5,956 gfx:3,242