Use 7 driver if you can find one. If not, install the Vista driver in compatibility mode for Vista. Compatibility mode may cause it to install correct and recognize the device. Good luck.
If still no go, install by right clicking on that unknown device and choose update driver software. Browse my computer, let me pick, have disk, browse. Now find the .inf to the driver. Extract driver contents from rar or zip file beforehand if need be. Or if install file is .exe, let it extract to temporary folder first by running it. Then install with device manager as I said.