File Verifier++ is a useful Windows application that can help you confirm that a set of files haven't been changed. Which may sound a little odd, but actually it has several worthwhile applications.
Do you regularly back up files to CD or DVD, for instance? These may become corrupt over time, but usually there's no way to tell this. File Verifier++ can generate digital fingerprints called hashes for each file, though, and then save these on the discs as well. They may then be used at any time to verify that the backups are still good.
Or maybe you're concerned about malware? Create hashes for your Windows or Program Files folders, say, and that will help you spot any files that have been modified later.
And you might similarly use the program as an advanced troubleshooting aid. If you keep suffering PC problems every time you install a particular program, for instance, then hashes will let you know which system files it might have changed.
An Explorer shell extension makes the program easy to use, as you can generate hashes from the right-click menu for files and folders.
But there's also plenty of power available for experts, including support for more than 20 hashing algorithms, a command line version of the tool, and powerful search options that allow regular expressions.