No, you will not lose your NT 4 certification if you fail 70-240. You will simply have to take all of the Core Four exams instead--namely 70-210, 70-215, 70-216 and 70-217. However, if you fail 70-240 and don't pass all four of the other exams by 12/31/2001 (and meet other requirements for the Windows 2000 MCSE as well), you will indeed lose your NT 4.0 certification. However, that is because that certification becomes obsolete and invalid on 1/1/2002. For more information on this subject, visit the MCSE requirements page on Microsoft's Web site at http://www.microsoft.com/trainingandservices/default.asp?PageID=mcp&PageCall=requirements&SubSite=cert/mcse&AnnMenu=mcse.
This was first published in July 2001