And save the original keyboard layouts file with a different name. You can, for example, add a 1 to the registry file name so you have a backup.
Save the edited registry file of Keyboard Layouts (the original file name) back into to the registry. You can click on the file and it will reimport it into the registry replacing the kbd files in the registry.
Now reboot your Windows XP.
Now attempt to install KB2686509 again either via manual download going to http://www.microsoft.com/en-us/download/details.aspx?id=29804 and downloading from there or using Windows update again. It now should complete successfully.
If these instructions do not work for these orphaned DLL files, please post back on the http://answers.microsoft.com/thread/0deeacb6-115c-419d-ac37-03ff8927b79c thread with your exact problem.