Since the V3 doesn't make use of any AGP features I doubt that it's an AGP issue.
It smells like a bad card BUT you mentioned that the 3Dfx tab is missing and that sounds like a driver issue.
If you're overclocking the V3, don't for now.
First off you should be using the v1.05 drivers. Have them unzipped in a folder ready to use.
Try this:
- Go into Reg Edit and delete the 3Dfx registry entries in HKEY_CURRENT_USER\SOFTWARE and HKEY_LOCAL_MACHINE\SOFTWARE
- Do a file search in all folders under \WINDOWS and delete anything containing "3Dfx" or "Voodoo" including INF files.
- Go to Add/Remove Programs in Control Panel and remove anything having to do with 3Dfx, or Voodoo.
- Run MSCONFIG.EXE and uncheck anything in the Startup tab having to do with 3Dfx, Voodoo or your old 2D card. CAREFUL! Don't uncheck something if you don't know what it is! DO NOT ALLOW IT TO REBOOT!
- Go to Display Properties and change your video driver to Standard VGA.
- Restart and when it asks you for drivers, direct it to the folder with the new drivers.
- After it installs the drivers and reboots you need to run the SETUP.EXE program in the driver's folder to install the 3Dfx Tools (this adds the 3Dfx tabs to Display Properties).
Hope this helps...
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The Flying Penguin
http://TheFlyingPenguin.com