It looks like the D300 is not supported under CS3. The option I've seen suggested is the DNG converter to convert from newer camera formats to DNG format.
Thanks Tom. I will try that. If it doesn't work, I am going to simply kick punt my computer into the woods.
- Original contents deleted as the question was already answered by tachyonsc while I was composing my response
The DNG converter is a stand-alone application which is an alternative to Adobe Camera raw. Particularly useful when your camera is not covered by the latest version of ACR.
It does not go in any specific folder and you have to use it to convert your NEF files to DNG format in order to view them in Bridge and process them in ACR.
You really need to read the instructions on the download pages and in the links there before ploughing on to disaster!
I then downloaded DNG Camera Raw 4.6 zip from the Adobe site.
You goofed there. You need The DNG Converter 5.3. Always use the latest version of the DNG Converter. It is a stand-alone program that is in no way tied to your version of the ACR plug-in.
When you download the correct one, don't bury it in any folder in the Photoshop path.