Right, yeah, definetly some conflict.
I suspect you have two sound cards in your system (1 in PCI and one on the motherboard which is switched on (most motherboards have multichannel sound cards))
is the one you want a sound card in a PCI slot? Or one plugged into the motherboard? Or put another way, which one is the Yamaha sound card?
Have you got both turned on?
Right, delete all sound using the device manager again.
Now restart and go into Bios (del at bootup) and look for, 'onboard sound' in one of the menus and disable it.
Then reboot and hopefully it'll find the one in PCI (if this is the yamaha)
Unless the one in PCI is not the one you want, adn you want the one on the motherboard (if this is the Yamaha card), in which case, take the card out of the PCI slot out and re-enable the one on the motherboard.
As what this will be, is a confrontation as it were between 2 sound cards installed. Get me?
I hope this helps