The D7100 was not supported until the Camera Raw plug-in version 7.4 that was released this week. Adobe only supports their current version of a particular software application, where PSE10 is too old to have updates, anymore.
So you can , either:
Upgrade to PSE11 which is compatible with ACR 7.4, or
Download and use the free DNG Converter 7.4 to convert your NEF files that are too new for PSE10 into DNG files that are still raw but have enough information to be supported by your older PSE and ACR versions.
The DNGC 7.4 is available and currently near the top of the updates listed, here:
The DNGC converts an entire folder of files at a time so you need to point it to a folder, only, not an individual raw file.
For your older version of PSE and ACR, you will need to set a compatibility option to something older than ACR 7.1, otherwise the DNG files will be using a standard too new to work.