To check for conflict you go into the My Computer icon, open up Control Panel, Go into the System icon. Then open the Device Manager and look to see if there are any exclamation marks on any devices listed, especially the sound card. If there is, it is conflicting with another device, like a mouse or modem. At that point I would suggest highlighting the sound card and hitting "remove" at the bottom. Say yes to confirm it and then shut down your computer.
After you have it turned off, change the sound card to another slot on the board where it will fit, making sure it is firmly seated.
Then, restart the system and let it boot up and let W95 or W98 find it again. Then try to renistall the driver when it asks for it.
There is a way to manually change the device IRQ's and addresses in the Device Manager, but it can get tricky if your not sure what you are doing. Try the above first and see if that works. The more knowledgeble techs in this forum can walk you through the manual changes if it is necessary.