WMPNSCFG.exe is a legitimate process, which belongs to Windows Media Player. This process is responsible for launching the Windows Media Player Network Sharing Service (NSS) and waiting for notifications from that service. Once it finds new media devices, it designs a pop-up notification and warns people about them. If you click on this message, WMPNSCFG.exe will launch Windows Media Player, which will offer allowing or denying sharing. However, this process is not a key Windows process, so you can terminate it if you feel that it's causing you problems.
WMPNSCFG.exe may be used to hide malware! Hackers have started using the names of legitimate files in order to make people think that they are not infected, so there is no guarantee that WMPNSCFG.exe is not involved into this. If you found this process without installing Windows Media Player, you should be very careful with it. In this case, you should check the trustworthiness of this file with a help of RegCure Pro.