I took raw images on my Nikon D7200; downloaded the dng converter; converted a nef file to a dng file, but my Photoshop Elements 9 won't open it. Simply get a non responding message. Elements 9 has Camera Raw 6.1. Is it possible to open the dng file in Elements 9?
The DNGconverter does not work on individual files, you have to select a whole folder (not any of its files) to convert them in batch to the DNG raw format. The resulting converted files should open ok in your PSE9.
PSE7 being old can mess up. You might try looking for a nice (full) Photoshop-6.0 (or better) that has a RAW converter built in. You won't have a problem with converting single files, no batch converting. No need for a later version. Those who have it get a later version then sell 6.0.