This article was previously published under Q183840
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The Task Manager can be started by pressing CTRL+ALT+DEL and then clickingTask Manager on the Security dialog box. However, if there are many userenvironment variables defined, running Task Manager from the Securitydialog box may cause a STOP C000021A exception error message.
The System Environment Block becomes corrupted by the Winlogon service ifthe size of the User Environment is significantly large. This can also becaused by the installation of many applications on a system.
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack
Microsoft has confirmed that this is a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.