installing a cdrom and sound card

I am trying to get this hp 5/75 to take a upgrade. I have last drive=z in the config sys. Used different cables. As soon as i put in the sound card the network card stops working, the card is soft set no jumpers. So I removed the card and just tryedthe cdrom the system wont see it. And now it wont see half of the network drives. It says things like drive m is already in use.