1. Try to reinstall the driver for the 'Unknown Device' through Windows Vista. Click 'Start,' then type in 'device manager' in the 'Start Search' field. Press the 'Enter' key. Locate your 'Unknown Device.' (It should be listed under the already expanded 'Other Devices' header.) Double-click the 'Unknown Device.' Click on the 'Reinstall driver' button and follow the on-screen instructions.
2. Find a new driver by accessing the website of the manufacturer of the 'Unknown Device.' Return to the 'Device Manager,' and click on the 'Details' tab for information about the device if you are uncertain what the device is and who manufactures it. Copy and paste the 'Hardware IDs' results into your Web browser. Once you locate the manufacturer's website, search for the device and a Windows Vista-compatible driver. Download the driver, save it to your desktop and double-click it to install. Follow any on-screen instructions.

3. Uninstall and reinstall the device through the 'Device Manager.' Right-click on the device, and left-click on 'Uninstall.' Restart the computer, and allow Windows to redetect and reinstall the device.
4. Check your hardware against the Windows Hardware Compatibility List. Even though your device worked on Windows XP, it may be incompatible with Windows Vista. In this case, you must wait for a driver update from your hardware manufacturer, upgrade your hardware to a Vista-compatible device, physically remove the device from your computer, or disable the device through the Device Manager.