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How to Use WinDiff to Compare Registry Files

This article was previously published under Q171780
How can you compare registry entries before and after an upgrade, theinstallation of a new software package, or between two computers?
To use the Windows NT 3.51 or 4.0 Resource Kit utility Windiff.exe tocompare the differences between the registry entries before and after anupgrade, perform the following:

WARNING: Using Registry Editor incorrectly can cause serious, system-wideproblems that may require you to reinstall Windows NT to correct them.Microsoft cannot guarantee that any problems resulting from the use ofRegistry Editor can be solved. Use this tool at your own risk.
  1. Start Regedt32.exe.
  2. Select each registry root that you want to compare.

  3. From the menu bar, click Registry.
  4. Click Save Subtree As.
  5. Click Save as type.
  6. Select Text files.
  7. Save the file as Filename.old.
  8. Follow the above steps for all subtrees.
  9. Install the new software or perform the upgrade.
  10. After the upgrade or install repeat steps 2-6.
  11. Save the file as
  12. Run Windiff from the resource kit and compare the two files, filename.old and
NOTE: This procedure can be done for individual keys as well.

Article ID: 171780 - Last Review: 10/31/2006 19:00:14 - Revision: 1.1

  • Microsoft Windows NT Workstation 3.51
  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Server 3.51
  • Microsoft Windows NT Server 4.0 Standard Edition
  • kbhowto KB171780