So I presume you're implying that when you boot up in XP with your other HD, you do get soundy goodness?
I know you've been through a lot of drivers without any luck, but since you have that "unknwon named multimedia device", it's pretty clear that drivers are gonna be the way to go. Have you tried any generic ones with it, maybe, see if they give you a starting point?
Also, it's possible the drivers you downloaded rely on all of Windows 98 Updates to be present, I don't know if you can still get those from the Microsoft website anymore, but, do you have them all from anywhere?
I know you've been through a lot of drivers without any luck, but since you have that "unknwon named multimedia device", it's pretty clear that drivers are gonna be the way to go. Have you tried any generic ones with it, maybe, see if they give you a starting point?
Also, it's possible the drivers you downloaded rely on all of Windows 98 Updates to be present, I don't know if you can still get those from the Microsoft website anymore, but, do you have them all from anywhere?