I discovered that is is rather difficult to edit exif tags on photos. Its probably by design to prevent tampering of falsifying information.
I have been creating HDR photos with my Nikon D5000. It’s been a great success and good fun! However my HDR software keeps all the original exif info from the first image in the series. Some of the data is no longer relevant specifically the the exposure length or ISO! Can you imagine an HDR photo take at 1/1000 sec with a 200ISO? I think not!
Why does it matter? Well my over in my Photo Gallery it shows the camera settings at which each of the photos were shot. It bugs me that on those types of work it shows wrong info!
I spent some time searching and eventually came upon ExifToolGUI.
Allows you to edit / remove many exif tags
It takes a little effort to set it up, but here is a great tutorial of setting it up. But basically you have to place the command line ExifTool in the same directory as the ExifToolGUI app.