Anyone who has installed software on Windows XP has probably encountered a dialog box indicating that a particular application or driver is not certified for installation. That dialog box (which can be dismissed) is part of a relatively new program called File Signature Verification. The purpose of the program is to provide a means for reducing the number of driver incompatibility issues, which are probably the major cause of Windows system instability.

When a system or device driver file has the Microsoft digital signature, it is supposed to indicate that the files are both original and unaltered, as well as approved for Windows. Not only is this supposed to protect you from poorly written software, but it is also supposed to protect you from any virus' or hacker' gaining entry into your system by installing a modified system file.

File Signature Verification lets you identify the file's name, location, modification date, and version number. Open the program by entering sigverif into the Run dialog box from the Start menu. To check the digital signature, click on the Advanced button to open the Advanced File Signature Verifications Settings dialog box, then the Search tab, and search for Notify me if any system files are not signed to check for any Windows and all device driver files that don't comply; or Look for other files that are not digitally signed to search for files by type and location (non-system files).

The system has a logging function, and it's a good idea to use it. Having an historical log lets you view changes over time, and can be an aid in locating files that are bad actors, or ones that have been placed into your system with malicious intent. In the Settings dialog box, click on the Logging tab, and then click on the Save the file signature verification result to a log file check box. You can choose to append or overwrite the log file, as well as name it.

Barrie Sosinsky is president of consulting company Sosinsky and Associates (Medfield MA). He has written extensively on a variety of computer topics. His company specializes in custom software (database and Web related), training and technical documentation.