Which nikon camera are the files from?
If it is a newer Nikon you will need a newer version of ACR. PSE 10 stops at version 6.7. Adobe has progressed through 7.0, 7.1, 7.2, 7.3 and now 7.4. Adobe can't put the formulas in until Nikon provides them. There is always a delay. With some googling you can find where your camera falls on the list.
In PSE 10, go to the Help Menu and select updates. It will fetch ACR 6.7 for you. It your Nikon is included in that or earlier, you need to do nothing more.
If not, you get to pay the Adobe "camera update tax" and get the newer version of PSE that will accept the ACR 7.x series. When you do get it installed, you may still have to got to Help, Updates if your Nikon is so new that it is only included in the latest ACR.
What Nikon product is the NRW file from?
I have a Nikon P7700
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The Nikon Coolpix P7700 is newer than PSE10 can be updated to support. Specifically, the P7700 started to be supported with Adobe Camera Raw version 7.2. PSE10 only was updatable to ACR 6.7, I believe, so to read your P7700 files in PSE, you need PSE11.
An alternative is to convert the NRW files to DNG files using the current Adobe DNG Converter and open the DNGs in older camera-raw versions. You will want to be sure to set the DNG Compatibility options in the DNGC to something that ACR 6.7 can understand, which would be ACR 6.6, not the ACR 7.1 that it defaults to the first time you run it.
You can download the current DNG Converter, from the regular Adobe Updates page:
Thanks a lot. I will try this.