Validate File Extensions

Program files frequently vanish from Windows machines. Although essential to a program or tool, .exe, .dll, and other files commonly disappear. Users installing and uninstalling applications are often the culprit. They might upgrade an application by installing a new version on top of their existing version or try to remove the existing version by simply deleting its files. Viruses and their ilk can also delete files—as can hard-drive corruption and even system-cleanup utilities.

Whatever the cause, when a file disappears, its file-extension mapping is often broken. A file-extension mapping tells Windows what program to run when you double-click a file that has a particular file extension. Double-clicking a .doc file launches Microsoft Word, for example, and double-clicking a .pdf file runs Adobe Acrobat. Few things drive users crazier than trying to open a file whose file extension has become unmapped.

One way to gauge a machine’s health is to monitor for broken file-extension mappings. Ideally, all file extensions are mapped to some application, and if the application is missing, the file extension is unmapped. This month, I show you a Perl script that examines file mappings to determine which are broken, or orphaned. With this information, you will know which software you should reinstall or properly remove to fix orphaned file-extension mappings. . . .