http://www.Digital Camerasoft.com/softnamexif.htmlNamexif™ is a tool to automatically rename photos with the date they were shot.
Digital cameras have their own clock and record the date to each photos with a precision of a second. Since the date and time is recorded for each photos (provided it is an EXIF compliant digital camera), Namexif™ is able to rename these photos according to the date.
Doing so will:
make chronological order same as alphabetical one,
set a unique name to your photos
Have not tried, but seems good, also has the option to save the original file name at the end of the new file name
best bit is it's free!