This is the Microsoft Eradication Society. This is not a Windows Help and Support forum. If you need help doing something with Windows, next time go to a forum like
www.annoyances.org or
www.winguides.com . Here we discuss what is wrong with Microsoft Corporation, and alternatives to their software.
However since I'm nice I will reply to your question. By Windows NT 5 I suppose you mean Windows 2000. Explorer.exe is the Windows shell, not just a file manager. This means that if you disable it from starting up, you will not have a desktop, a taskbar, or a start menu. There will just be an empty screen unless you tell Windows to use a different shell. If that is what you want to do, then run the file gpedit.msc and use the System Shell policy to specify what shell you want to use. Other than that I do not think there is a way to disable Explorer from starting up. You might want to try to see what happens if you just delete the file, though.