Well... NVIDIA drivers that are on www.nvidia.com only works up to GeForce 3. The only solution is to upgrade to Mandrake 9.0 or 9.1!

Is there some problem with earlier versions of Mandrake that restrict those drivers? Because I was able to get my GF4s working in RedHat 7.3 and 8.0 (along with Debian Woody, its derivitives, and Gentoo) with the drivers from the nvidia website. Just use the source code and you shouldn't have any issues.
 
Now, with being dropped back to the desktop, did you go through the readme on it and comment the "dri" and "GLcore" lines in it? Also, did you change the "vesa" or "nv" line to "nvidia" (it would be the "driver" line")? These are in your X config file, which should be at /etc/X11/XF86Config or possibly /etc/X11/XF86Config-4 (if you have a "-4" one, that's the one that you will be probably using). Here is what my XF86Config-4 file looked like on one of my systems with a GF2 MX and a 17" monitor (this file was generated by DEBCONF in Debian, and worked pretty well but is still very basic). Pay special attention to the lines that are in bold, as those were the lines I had to change:
 
 
### BEGIN DEBCONF SECTION
# XF86Config-4 (XFree86 server configuration file) generated by dexconf, the
# Debian X Configuration tool, using values from the debconf database.
#
# Edit this file with caution, and see the XF86Config-4 manual page.
# (Type "man XF86Config-4" at the shell prompt.)
#
# If you want your changes to this file preserved by dexconf, only make changes
# before the "### BEGIN DEBCONF SECTION" line above, and/or after the
# "### END DEBCONF SECTION" line below.
#
# To change things within the debconf section, run the command:
# dpkg-reconfigure xserver-xfree86
# as root. Also see "How do I add custom sections to a dexconf-generated
# XF86Config or XF86Config-4 file?" in /usr/share/doc/xfree86-common/FAQ.gz.
 
Section "Files"
FontPath "unix/:7100" # local font server
# if the local font server has problems, we can fall back on these
FontPath "/usr/lib/X11/fonts/misc"
FontPath "/usr/lib/X11/fonts/cyrillic"
FontPath "/usr/lib/X11/fonts/100dpi/:unscaled"
FontPath "/usr/lib/X11/fonts/75dpi/:unscaled"
FontPath "/usr/lib/X11/fonts/Type1"
FontPath "/usr/lib/X11/fonts/Speedo"
FontPath "/usr/lib/X11/fonts/100dpi"
FontPath "/usr/lib/X11/fonts/75dpi"
EndSection
 
Section "Module"
# Load "GLcore"
Load "bitmap"
Load "dbe"
Load "ddc"
# Load "dri"
Load "extmod"
Load "freetype"
Load "glx"
Load "int10"
Load "pex5"
Load "record"
Load "speedo"
Load "type1"
Load "vbe"
Load "xie"
EndSection
 
Section "InputDevice"
Identifier "Generic Keyboard"
Driver "keyboard"
Option "CoreKeyboard"
Option "XkbRules" "xfree86"
Option "XkbModel" "pc104"
Option "XkbLayout" "us"
EndSection
 
Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/input/mice"
Option "Protocol" "ImPS/2"
Option "Emulate3Buttons" "true"
Option "ZAxisMapping" "4 5"
EndSection
 
Section "Device"
Identifier "Generic Video Card"
Driver "nvidia"
EndSection
 
Section "Monitor"
Identifier "Generic Monitor"
HorizSync 30-85
VertRefresh 48-120
Option "DPMS"
EndSection
 
Section "Screen"
Identifier "Default Screen"
Device "Generic Video Card"
Monitor "Generic Monitor"
DefaultDepth 24
SubSection "Display"
Depth 16
Modes "1024x768" "800x600"
EndSubSection
SubSection "Display"
Depth 24
Modes "1024x768" "800x600"
EndSubSection
EndSection
 
Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"
EndSection
 
Section "DRI"
Mode 0666
EndSection
 
### END DEBCONF SECTION
 
 
Next, make sure that you're nvidia modules are available for loading (I think the RPMs take care of that, but usually it will deal with a module-loading file (modules.autoload for example). Try this file first, as it's usually the one that hangs everyone up. One more thing: make sure that your refresh rates are correct, as that can cause the same problem (although you usually see flashes of it trying to load, and can hear the gun in the monitor clicking away as it tries different refresh rate/resolution combos).

I remember that the XFree http://www.nvidia.com/view.asp?IO=linux_display_ia32_1.0-4191 should fix this.