I donno if the default xf86config would help or not, but do give it a try, but please back up your /etc/X11/XF86Config or XF86Config-4 file (just cp it to some other name)
when u are in the login screen, press ctrl+alt+1 to go to tty01 and login there (as root) then type xf86config. follow those instructions. if you are really good at editing that cursed file
use an editor and edit the device section and make it choose the geforce 4 generic chipset there... i donno the proper parameters, i guess some of us can help u here.
after u think you're done, get back to the X server by pressing ctrl+alt+f7 and login, then type X or startx or xinit, you should be in there.