If you open device manager in windows on your computer, you may see some of the entries under devices list.
There could be some devices in the list which are shown as unknown devices in device manager.
A small freeware called Unknown Devices lets you find out those unknown devices in Device Manager really are, so that you can install appropriate drivers for those devices
Unknown Devices extract each piece of information about the from the device manager about the unknown devices.
It supports Win95, 98, 98se, XP and 2003 but not Windows NT and it is free for personal and professional use. This program is free from any spyware, adware, malware, popups etc.
In order to run device manager you will need the latest version of pcidevs.txt to be placed in the same folder where you extract UnknownDevices.exe
Note: copy and replace the latest pcidevs.txt with the one which comes in the zip archive of unknown devices.