This issue can occur if you accidentally delete the Oemnxptc.inf file. If you delete the file, the registry key is also deleted automatically when you start the Network tool in Control Panel.
Manually expand the Oemnxptc.in_ file from your original Windows NT CD-ROM to Oemnxptc.inf in the %SystemRoot%\System32 folder. If this does not resolve the problem, you may need to add both the Oemnxptc.inf file and the registry key manually. If that does not resolve the problem, you must reinstall Windows NT.