What version of what program are you using ACR 7.4 with?
According to Adobe's camera-support list, you need ACR 8.3 for the D5300:
Which probably only works with PS-CS6/CC and PSE 12/13.
If you're using software older than PSE12 or PS-CS6 then you can either upgrade to the current versions with their newer minimum-OS-version requirements or download, install and use the DNG Converter 8.3 or newer to create DNGs from your NEFs and those DNGs will work in ACR 7.4. The DNG Converter is available from Adobe's Updates page: http://www.adobe.com/downloads/updates/
I'm using Photoshop Elements 11, but the thing is that is did work a while ago
ACR 7.4 will not open raw files (NEFs) of a Nikon D5300. Is the camera model in the thread title wrong and you have a D5200? The options for D5300 NEFs are listed in my previous reply.