I have GeForce 2 hualhead and have two Flatscreens hooked up and working in Linux, only in X tho, in console only one can work, or you can have both working in "stereo" being mirrors of each other but thats useless.
So you want both monitors in X? OK, it's not very difficult, maybe an hour of work.
First thing download NVidia drivers and install them, make sure they work and configure your monitor. Then go over to NVIDIA again and read the big README file they have about Linux drivers, pay extra attention o twinView, i think its in one of the appendices.
Then head over to www.geocities.com/nskl86/XF-TwinView.txt
and look through my XFConfig file for TwinView. Then eaither copy and modify my file, or edit your own to look like it.
NOTE: I had to speify NvAgp option in "Device" section, or else my system freezes, you might not need this line:
Option "NvAgp" "0"
It.s under the Nvidia device section.
Ok, i think thats all, good luck and ask if you have problems.