A better method is to use WinDiff.exe.
Windiff.exe is installed from the Support Tools folder on the Windows 2000 or Windows XP CD-ROM, or from the Windows NT 4.0 Resource Kit or Supplement 4, but I find the Windows XP version to work better.
To locate changed registry entries:
1. Use Regedit.exe to Export all or a portion of the registry to an original.reg file. Use the Win9x/NT4 Registration Files (REGEDIT4) format.
2. After making the registry change, or application install, Export the same branch that you used in step 1 to a changed.reg file, using the Win9x/NT4 Registration Files (REGEDIT4) format.
3. Open WinDiff.exe and use the File menu to Compare Files.
4. At the Select First File dialog, browse to and double-click the changed.reg file.
5. At the Select Second File dialog, browse to and double-click the original.reg file.
6. Highlight (select) this comparison and press the Expand button. The first difference will be highlighted. Red items (<!) are deleted from the original file. Yellow items (!>) are inserted in the original file. Changes are a indicated as deletions and insertions.
7. To view the next difference, press CTRL+F8. To view the previous difference, press CTRL+F7.