Keeping your word is normally considered a virtue. When you're Microsoft, it can be construed as stubbornness. Gartner analysts Michael Silver and Neil MacDonald used the occasion of last week's unprecedented Microsoft security bulletin package to argue that Redmond is making a big mistake by sticking to its policy on Windows NT Workstation 4. Microsoft stopped offering free fixes for the desktop operating system when support expired on June 30. From a business standpoint, the tough-love approach on NT4 makes sense. Microsoft is going to have a hard time nudging customers off NT4 if they can still get freebies. In this case, however, Gartner is right. We're not talking about office furniture here, we're talking corporate livelihood.If an enterprise network is crippled by a virus because Microsoft withheld an NT4 security patch that it had already created for its paid-support program, the outcry will be heard far and wide. Gartner figures that 10% to 20% of enterprise PCs still run NT4, so chances are good that someone is bound to get burned.