I have a 2.8 P4 and a Nvidia FX 5500 AGP graphics card. I've installed Xubuntu 10.04. It is WAY too laggy with the default o/s driver. Installing the Nvidia 173 driver, modaliases and nvidia-settings packages via synaptic package manager results in the following error message:

An error occurred, please run Package Manager from the right click menu or apt-get in a terminal to see what is wrong. Error: Opening the cache (E::read, still have 11898251 to read but none left, E: The package lists or status file could not be parsed or opened.) This usually means that your installed packages have unmet dependencies.

When restarting the PC the resolution drops to 800x600 (from the monitors native 1440x900).

Nvidia settings cannot be changed either from the Xfce menu or Nvidia Xserver. Nvidia Xsever gives the following error message:

You do not appear to be using the Nvidia X driver. Please edit your x configuration file (just run 'nvidiaxconfig' as root ) and restart X server.

Also, I can't find anything in any directory called xorg.