More file association work.

- Add an OpenWithProgids value. The default value of ".iss" is still being set, though it doesn't appear to have an effect on Windows 11 (the association works without it, and changing it doesn't change the default app).

- Remove OpenWithInnoSetup verb (likely predates the "Open with" menu)

- Unregister before registering. This removes the OpenWithInnoSetup verb on existing installations.

Projects/Src/IDE.FileAssocFunc.pas

@@ -67,19 +67,19 @@ function RegisterISSFileAssociation(const AllowInteractive: Boolean; var AllUser
   if not Result then
     Exit;
 
+  { Remove any cruft left around from an older/newer version }
+  UnregisterISSFileAssociationDo(Rootkey, False);
+
   SelfName := NewParamStr(0);
 
   SetKeyValue(Rootkey, 'Software\Classes\.iss', nil, 'InnoSetupScriptFile');
   SetKeyValue(Rootkey, 'Software\Classes\.iss', 'Content Type', 'text/plain');
+  SetKeyValue(Rootkey, 'Software\Classes\.iss\OpenWithProgids', 'InnoSetupScriptFile', '');
 
   SetKeyValue(Rootkey, 'Software\Classes\InnoSetupScriptFile', nil, 'Inno Setup Script');
   SetKeyValue(Rootkey, 'Software\Classes\InnoSetupScriptFile\DefaultIcon', nil, SelfName + ',1');
   SetKeyValue(Rootkey, 'Software\Classes\InnoSetupScriptFile\shell\open\command', nil,
     '"' + SelfName + '" "%1"');
-  SetKeyValue(Rootkey, 'Software\Classes\InnoSetupScriptFile\shell\OpenWithInnoSetup', nil,
-    'Open with &Inno Setup');
-  SetKeyValue(Rootkey, 'Software\Classes\InnoSetupScriptFile\shell\OpenWithInnoSetup\command', nil,
-    '"' + SelfName + '" "%1"');
   SetKeyValue(Rootkey, 'Software\Classes\InnoSetupScriptFile\shell\Compile', nil, 'Compi&le');
   SetKeyValue(Rootkey, 'Software\Classes\InnoSetupScriptFile\shell\Compile\command', nil,
     '"' + SelfName + '" /cc "%1"');
@@ -112,6 +112,16 @@ procedure UnregisterISSFileAssociationDo(const Rootkey: HKEY;
     end;
   end;
 
+  procedure DeleteValue(const Rootkey: HKEY; const Subkey, ValueName: PChar);
+  var
+    K: HKEY;
+  begin
+    if RegOpenKeyExView(rvDefault, Rootkey, Subkey, 0, KEY_SET_VALUE, K) = ERROR_SUCCESS then begin
+      RegDeleteValue(K, ValueName);
+      RegCloseKey(K);
+    end;
+  end;
+
 begin
   if Conditional then begin
     const ExpectedCommand = '"' + NewParamStr(0) + '" "%1"';
@@ -125,11 +135,14 @@ procedure UnregisterISSFileAssociationDo(const Rootkey: HKEY;
   RegDeleteKeyIncludingSubkeys(rvDefault, Rootkey,
     'Software\Classes\InnoSetupScriptFile');
 
-  { Leave '.iss' as-is. Other apps may have added their own OpenWithProgids
-    values there, and Microsoft docs recommend against trying to delete the
-    key's default value (which points to a ProgID). See:
+  { As for '.iss', remove only our OpenWithProgids value, not the whole key.
+    Other apps may have added their own OpenWithProgids values there, and
+    Microsoft docs recommend against trying to delete the key's default value
+    (which points to a ProgID). See:
     https://learn.microsoft.com/en-us/windows/win32/shell/fa-file-types
   }
+  DeleteValue(Rootkey, 'Software\Classes\.iss\OpenWithProgids',
+    'InnoSetupScriptFile');
 
   { Remove unnecessary key set by previous versions }
   RegDeleteKeyIncludingSubkeys(rvDefault, Rootkey,