Open File Signature Verification
On the Search tab, click one of the following:
Notify me if any system files are not signed
Checks only the Windows system files and all device driver files to see if they have a digital signature.
Look for other files that are not digitally signed
Enables you to specify the file type and location of non-system files to check for a digital signature.
Click OK, and then click Start.
To start File Signature Verification, click Start, click Run, type sigverif, and then click OK.
Write digital signature information to a log file
Verify that system files have a digital signature
Using File Signature Verification