When you run the File Signature Verification utility (Sigverif.exe) on a Microsoft Windows XP-based computer, the utility may stop responding (hang).When you open Task Manager and then click the Applications tab, File Signature Verification is listed as Not responding in the Status column.
This problem may occur in if an unsigned driver is installed on the computer.
To work around this problem, use either of the following methods.
Try running the File Signature Verification utility again. To do this, follow these steps:
Press CTRL+SHIFT+ESC, and then click the Applications tab.
Click File Signature Verification, and then click End Task.
Click Start, click Run, type sigverif.exe, and then click OK.
Check the logs directly. To do this, click Start, click Run, type %SystemRoot%\sigverif.txt, and then click OK.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.