Due to the way Oracle initially packaged JavaFX, it's important to get the right version. Open a command window and type "java -version" if you're unsure which one you need. Extract the folder from the zip file. Double-click the PhotoGrok icon.
Oracle has disabled self-signed web start applications in the latest versions of Java. To use this version, type "javaws -viewer" and open the "Security" tab. Add "http://www.haplessgenius.com" to the Exception Site List. You only need to do this once. A security confirmation dialog will appear in later versions of Java.
PhotoGrok categorizes photos and other files by metadata (and a whole lot more). It's powered by Phil Harvey's excellent ExifTool. Java 6 or higher is required. Please read the FAQ and check out the scripting examples.