Using file compare to see changes made to the registry
If wanting to see what registry entries are modified when performing a certain action, then one can use the Registry Editor to export the Windows registry before before performing the action and export after having performed the action.
Then one can use the file compare utility to see what changes have been made:
FC before.reg after.reg > diff.txt
Note when exporting the registry hives in Windows 2000,XP,2003 then they are exported as unicode (Windows Registry Editor Version 5.00). To perform a file compare on two unicode files:
FC before.reg after.reg /U > diff.txt
Note instead of exporting the registry, then one could also use Process Monitor by SysInternals.com to see the registry changes made by an application.