Windows finds, then loses, sound cards

Hello,

I have a problem that I haven't seen here yet, although I expect it is
here somewhere.

I have a desktop PC, 350 MHz, running Win98SE.

One day it "lost" the sound card. I re-installed it, and went through
all the steps of installing drivers. Windows said it was installed
correctly.

But when I try to *use* the sound card, Windows Media Player comes on,
then I get an error message that says:
"Windows Media Player cannot play the file because there is a problem
with your sound device. There may not be a sound device installed on
your computer, it may be in use by another program, or it may not be
functioning properly."

So I put in a different sound card. Same error message. This has now
happened for 4 sound cards in 4 different slots ( 2 ISA, 2 PCI ).

Now here are the questions:
1. Is the problem more likely to be in . . .
(a) the motherboard, not connecting properly with the sound card?
(b) the interrupts or some similar resource?
(c) Windows 98?
(d) Windows Media Player?

2. What can I do about it?

Thank you for all replies!

Ted Shoemaker