Make sure you unzip the drivers to an obvious place on your hard drive - ie make a folder on C: (or your main Hard drive) and call it Sound Driver. Then in device manager, right click on the unknown device, and press update driver. Then follow the wizard, but use the "Install the software from a specific location" option, and the "Don't search, I will choose the driver to Install" option. Then click on the "Have Disk" button, and choose the driver from the folder you made earlier.
If that still doesn't work, then download Everest Home Edition, (search on Google), and that software should be able to find out what your soundcard is. Then you can search for drivers on the net.
Hope that helps.