I too run a V3/V1 setup with an Orchid Righteous 3D. It's very doable and gets you 100% compatibility with glide games. There are two methods to make this work:

1 - Reinstall the V3 drivers and reboot to make it the "dominant" card. Likewise, reinstall the V1 drivers to make it the "dominant" card. Don't use the Voodoo 1 reference drivers. Use the official Orchid v3.01 driver, "RIGHT301.EXE". Strangely, FalconFly.de doesn't appear to have this. For the V3 card, use the reference v3.01 drivers.

2 - Copy the V1 glide dll files to your game's directory if you want it to run on the V1: GLIDE.DLL, GLIDE2X.DLL, GLIDE2X.OVL, SST1INIT.DLL. Likewise, copy the V3 glide dll files to your game's directory if you want it to run on the V3.

Note that static-link games such as EF2000 should always run on your V1 card, even if you don't install the drivers for it. If EF2000 won't run, there's a problem somewhere else.

Also, check this thread for more info:
a 3dfx voodoo guide

Also, this:
Glide 2.1.1 games and Voodoo 2

Also also, this:
Voodoo5 + Voodoo1 Combo

Personally, I use and prefer method #1. I remember trying method #2 and not having luck with it, but I can't remember what game gave me a problem or what the details were. Most people use method #2 and have no issues. Perhaps I'll try it again sometime.

Also, note that some games such as Expendable and Incoming have issues with CPUs faster than 450mhz. Underclocking to 500mhz is a good idea. My system runs a Celeron 600 and I haven't had any problems, but I also don't run Expendable or Incoming. FWIW, EF2000, Archimedean Dynasty (aka Schleichfahrt), and MechWarrior II 3DFX all run flawlessly on my system. Make sure you've got your AGP and PCI dividers set correctly after underclocking. Also, try moving your V1 card to a different slot.

Edit: My system is running DirectX 9.0c - 08 Dec 2006. It was the last Win98SE version. However, I agree with what Deksor wrote below. In hindsight, I wish I would have just left DirectX v8.1b installed.

I would add to this : don't install directx 9, it makes incompatibilities with older games. Most DX9 games won't work great with that hardware configuration anyways, stick to DX8 and you should be good

1 - Reinstall the V3 drivers and reboot to make it the "dominant" card. Likewise, reinstall the V1 drivers to make it the "dominant" card. Don't use the Voodoo 1 reference drivers. Use the official Orchid v3.01 driver, "RIGHT301.EXE". Strangely, FalconFly.de doesn't appear to have this. For the V3 card, use the reference v3.01 drivers.

So DirectX and OpenGL will run on the "dominant" card by default.
That is strange, I was careful to install Voodoo 3 drivers last, but it didn't do a thing.
I'm going to reinstall Windows and try again.

Personally, I use and prefer method #1. I remember trying method #2 and not having luck with it, but I can't remember what game gave me a problem or what the details were. Most people use method #2 and have no issues. Perhaps I'll try it again sometime.

Since I only want a Voodoo Graphics for statically-linked games like EF2000 and DOS games Shadow Warrior, do you think it would be ok if I kept the drivers that come with Windows 98SE for the Righteous 3D, and copied the Glide files for each game requiring them?
I'm thinking Windows 98 SE comes with WHQLed, specific drivers for the Orchid Righteous 3D, and they are 2 years newer than the latest Orchid drivers.

I would add to this : don't install directx 9, it makes incompatibilities with older games. Most DX9 games won't work great with that hardware configuration anyways, stick to DX8 and you should be good

That is a good idea, I don't think any of the games I'm trying to run use DirectX 9 anyway.
I'll just install DX 8.1.

Thanks a lot for your help!

I've been trying to make it work since my last post without any luck.

I installed Windows 98 SE from scratch, installed the Righteous 3D drivers, next the Voodoo 3 drivers, and then DirectX 8.2.
I installed Dungeon Keeper Gold and the Direct3D patch for testing.
I copied GLIDE3X.DLL in Dungeon Keeper's install folder and launched the game.

GUI show OK, but most graphics in game are colored white with lots of artifacts.
Reinstalling Voodoo 3 drivers again didn't do anything.
The glide file didn't do a thing, since Dungeon Keeper is a DirectX game.

I haven't checked any OpenGL games yet.

I'm not sure what my next step should be...

Don't use DX 8.2. That version should only be used if you have an online gaming problem that has been identified as being fixed with DX 8.2. You should use DX 8.1b.

Have a look at my Win98SE install guide here.

Create directories:
c:\voodoo\v1
c:\voodoo\v3

Extract your Orchid drivers to "c:\voodoo\v1" and your Voodoo 3 drivers to "c:\voodoo\v3".

Read the instructions and install your Orchid Righteous 3D drivers normally, then reboot twice.

Read the instructions and install your Voodoo 3 drivers normally, then reboot twice.

Now, you can choose to use either the Voodoo 1 or the Voodoo 3 by reinstalling the driver for the one you want.

For Voodoo 1
Start -> Settings -> Control Panel -> System -> Device Manager -> Sound, Video and Game Controllers -> Righteous 3D -> Driver -> Update Driver -> Next -> Display a list... -> Next -> Have Disk -> C:\Voodoo\V1 -> Righteous 3D -> OK -> Yes -> Next -> (Keep existing files for all prompts) -> Finish -> Yes (Reboot Now)

For Voodoo 3
C:\Voodoo\V3\setup.exe

Let us know if this helps or not.

I'm having some success at last!

A couple of games are still sorta stuck , but I think I'll be able to manage, thanks to your help.