Try pulling out your sound card and see if you can play the game. If that works, see if you can find a different sound card, or buy a different one if you can afford it.
You DEFINATELY had a problem before with the sound card in PCI 1, that one shares with your AGP slot.
Go to Start | Programs | Accessories | System Tools and choose "System Information".
Now in the left pane, expand Hardware Resources, and then click on IRQs. Copy the results and paste them in a message here for starters. We'll see from there.
Oh, and you should definately be using the Detonators for that thing.
http://dangerousdog.com/downloads/dets/index.htm I'm not sure which ones are the best on 98, but I'd start with the latest "official" ones, the 12.41's.