Double clicking PS files opens Photoshop but not the file? why?

Mac OSX 10.4.11 - Adobe Photoshop 8.0

Since re-installing my system a few months ago double clicking on a photoshop doc will open Photoshop itself but not the file I have clicked on - can't work out why. Can anyone help? Any file wherever its saved the same thing happens.
Thanks

this is covered in the FAQs

And here < http://www.ninisworld.com/thecorner/tutorials/photoshopopen. html> including download of the file you need to add.