Driver Verifier Manager is a tool present in Windows XP and Vista both. Using this tool you can verify if an unsigned device driver works with Windows or not. To open this tool, click on Start Menu → Run, type verifier and press Enter. A window would open as shown below :
There are many options. To verify, you can choose the first option from the top in the option list and click Next. In the next screen you are given option to manually choose drivers or automatically select the unsigned drivers, drivers designed for older versions of Windows or all driver as shown below :
Select the last option from the top and click Next. You will see all of the loaded drivers. If you think a particular driver is malfunctioning you can choose that driver (check the checkbox in front of that driver) and click Finish. A message box will show telling you to restart Windows.
If your selected driver is not working properly then upon restart you would see a Blue Screen with error message. If the selected driver is working properly, then Windows will start normally.
To reset the verifier, open Start Menu → Run, type verifier /reset and press Enter.