Download the latest S/card driversremove anything to do with the soundcard i.e drivers etc..
Remove the card...
go into the BIOS and disable com2 (serial 2)
that will free an IRQ slot.....
reboot , install the USB device....
shutdown put the S/card in PCI slot 3 ...
reboot while crossing your fingers that it will go on to a different IRQ 
Also some boards have the option to assign an IRQ to a PCI slot , never used it but its another choice