I think I might know what's wrong. I hope this helps anyway: I understand that you are using a GF2 video card, and that your sound card is inserted in to PCI slot number 1. And your GF2 is an AGP card. The AGP port and PCI slot number 1 share the same IRQ. It's important not to use PCI slot number 1 for a typical sound card, because of this reason. Try the sound card in PCI slot number 2. A great place to put one of your Voodoo2 cards is in PCI slot number 1, because it needs no IRQ! 😀

Wow that's some great advice!

No the Sound Card is not on PCI Slot 1. It's on PCI Slot number 4 or 5 actually.
Thanks for the advice though!

I've run into this problem on occasion before too... not all PCI slots are created equal 😀
Often its not just slot 1 that has a shared IRQ, sometimes there are other slots that do it too.

I've just had a look at your manual and on page 28 it explains the the slots that share IRQ's.

The manual is here http://www.motherboards.org/files/manuals/1/cusl2-102.pdf
For this board it appears that slot 1 and 5 share an IRQ; slot 3 shares with USB; slot 4 shares with LAN, while 2 and 6 do not share IRQs.

So I'd try moving your PCI cards around so one is in slot 2, one is in slot 6, and either slot 1 or 5 is populated (not both).
In the BIOS I'd make sure you have disabled everything to do with onboard audio (if applicable) and also if you aren't using usb keyboard/mouse, disable legacy USB.
Also, another thing to try, find what IRQ your sound card is using and in the PnP settings in your BIOS set that IRQ number to Reserved. Also make sure you have the latest BIOS installed for your motherboard.

Well typically there is a lot of IRQ sharing. For example, 440BX only has 4 IRQs available for PCI and AGP together. USB is on one of these too as are any other integrated PCI devices like a sound chip or RAID controller. Every other PCI slot shares and PCI slot 1 shares with AGP. If there's a sixth PCI slot it will be a slave slot without busmaster support due to a 440BX PCI limitation and you can only use some cards in it.

It's not a big deal and you don't lose performance unless you stick two very busy devices together. Some cards just don't get along because they aren't properly designed or the motherboard isn't well designed. I'd make a list but I've seen problems with just about every type of card so there's no point. 😉

For example, this is how a Abit BF6 works:

I had similar issues. Did the MPU401 and SB pro emulation install after you fixed the correct file?

You are supposed to remove the drivers completely then install the modified drivers you just did. I took an extra step and used driver cleaner 2.7 to remove the drivers. After I installed again the other items installed and Dos was working for me.

Well I tried all of the above with the same results. I tried installing the card to Slot 6 and assigning the IRQ I found in Windows manually to the Slot. Same shit.
Yeah RogueTrip, I even formatted the Hard Drive and made a clean install of Win98SE just to make sure.

Btw, I've got the latest, non beta bios.

Maybe the card is simply faulty...

Nah, I don't think the card is the problem. I managed to make DOS work perfectly, by reserving IRQ 5 and IRQ 11 in the BIOS.
It doesn't hang anymore which is nice. I'm not really THAT interested in 3D sound, but since I've been hearing so much about it on the Vortex 2 I'd like to see what the fuss is all about. Otherwise, DB50XG Midi playback and nice DOS support is fine for me.

The thing that bugs me is that the 3D demos work and they sound quite nice. The only game I found to be working properly(I think) is Populous III, but since it's a strategy game, the 3D effects weren't all that great.
Let me recap and add a few other games to the list:

Half-Life : Sounds almost the same as non-3D
Jedi Knight : A lot of sound loss, 3D effect just doesn't work
Need For Speed III (through EAX support) : Same as non-3D
Rayman 2 : Installed a supposed A3D sound patch, music doesn't play at all, no 3D effects
Populous III: Seems to work fine with 3D effects
Shogo M.A.D. : 3D effects seem to work ok, but they do feel shallow, maybe it's just me
Blood II : 3D effects seem to work ok, but they do feel shallow, maybe it's just me
Unreal : 3D effects don't work

I should note that I'm using the latest drivers and patches, as well as the latest A3D driver.

EDIT: Ok wow, I tried Jazz Jackrabbit 3 Alpha just for fun and the effects work on it and sound great. So let me get this straight, a game in Alpha state works better than all released games with patches?
Hilarious...

Can you try the card in another motherboard?

Half Life has A3D 2.0 support and is probably the best use of it. But you have to get to certain action-packed areas to notice the effects. Although the low fidelity of the sound samples kinda sucks. They sound like 22kHz at best, maybe 11kHz even. Half Life felt kinda behind the times in a lot of technical ways.

JK has A3D 1.0 support and this does give the game a bit better atmosphere.

The NFS A3D is interesting too. Be sure to turn on the geometric reverb option in the Aureal control panel. This provides environmental effects like EAX too.

Unreal's 3D audio has never worked well in my experience.

In my opinion, the highlight of Vortex cards is their 2 speaker spatialization. The effect sounds like you are encompassed by audio. It was definitely the best 2 speaker audio of the time. The A3D 2.0 effects are neat in some games too but they are rare and they were very demanding on the CPU.

Nah I can't use it on another PC unfortunately 🙁.
Oh well, I can't say I really care anyway, DOS is working fine and I've finally got some awesome MIDI with the DB60XG attached on the card.
That's all I need 😁