Perhaps you should look in C:\WINNT\System32\NSLOOKUP.EXE then. To me that looks like a factory floor install of NSLOOKUP. It is available in NT4, Windows 2000 Professional/Server/Advanced Server, Windows XP Home/Professional and Windows 2003 (.NET).
I don't know who wrote it or what OS originally had it and I care even less. The fact remains that it is available in the above-listed OS's.
