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Last Updated On: 08/05/2004

Windows NT Service Pack 5


This release of Microsoft Windows NT 4.0 Service Pack 5 (SP5) is easy to apply while Windows NT is running. SP5 updates all files that are older than those included in this Windows NT Service Pack. Service Pack releases are cumulative, containing all previous Service Pack fixes and any new fixes created after Service Pack 4.

IMPORTANT: It's recommended that you stop running any critical services before you apply Windows NT 4.0 SP5. For more preinstallation recommendations, see Section 2.1, "Before You Install the Service Pack."

IMPORTANT: SP5 contains only 40-bit encryption. This release isn't supported for installation on an existing North American 128-bit installation of Windows NT 4.0. If you install SP5 on a computer with 128-bit encryption, system services might fail to start.

To determine if 128-bit encryption is installed

  1. Open My Computer, click View, and then click Options.
  2. Click the View tab, select Show All Files, and click OK.
  3. Click Start, point to Find, and then click Find Files or Folders.
  4. Search for files named "Rsaenh.dll" on your local hard drives.
  5. If the file exists in the System folder in your Windows NT folder, then you have 128-bit encryption support installed. If the file does not exist, you have 40-bit encryption.

Installing the 40-bit version of SP5 on a previously existing 128-bit computer will not downgrade all of the encryption in the operating computer, so it will not necessarily change the exportability of the computer.

What Is Service Pack 5?

SP5 is a collection of current updates and enhancements to Windows NT Server 4.0 and Windows NT Workstation 4.0 since their releases.

The following is a list of the most frequently requested Windows NT 4.0 updates that are included in SP5:

  • DHCP Server of SP4 Ignores Reservations
  • SP4 forces cluster servers to be taken off and online
  • Windows NT 4.0 SP4 Does Not Update MTS Files
  • Duplicate SCSI Logical Unit (LUN) 0 When LargeLUNs Registry Key Enabled
  • Under stress, a computer running Windows NT Server or Workstation may display a STOP 0x0000001E error message on a blue screen.
  • Cannot configure ODBC logging when using Microsoft Data Access Components (MDAC) 2.0 SP1, SP4, and Proxy Server 2.0.
  • Secondary WINS query delayed by 1500ms even when primary WINS returns 'na
  • Using SP4, RCP "host:foo ." fails whereas RCP "host:foo foo"
  • SP4 systems access the hard disks every five minutes, which interferes with Power Management.

Y2K fixes

SP5 provides the latest fixes to known Year 2000 issues in Windows NT 4.0. For the latest information on Year 2000 and Windows NT 4.0, see the Microsoft Year 2000 Readiness Disclosure & Resource Center Web site at or call 1-888-MSFT-Y2K.

Updates to SP4 issues, including:

  • Reduced heap fragmentation issues which would lead to memory problems.
  • Eliminated memory fragmentation problem with Critical Sections.
  • Eliminated a system hang that could occur on multiprocessor systems with multiple memory maps.
  • Resolved SP4 issues with Oracle Fail Safe software for Windows NT Clusters.
  • Eliminated hanging issues when SetSecurityInfo and SetNamedSecurityInfo calls were made during DLLInit time.
  • Enabled Desktop folders in Explorer windows to retain settings.
  • Eliminated issues where LPD would stop the printing of multiple copies.
  • Prevented DNS from converting host names to lowercase.
  • Prevented GetHostbyName from returning unbound IP RAS addresses.
  • Eliminated issues where Apple Macintosh Clients can't see Windows NT 4.0 Server after upgrading to SP4.
  • Eliminated issues where changing an SFM password allows Windows NT client computer to share access with null password.

    Security updates

    SP5 contains current updates for known Windows NT 4.0 security issues. For the most recent information about Windows NT security, see the Microsoft Security Advisor Web site at