Windows error 127 is also known as iTunes error 7. It usually occurs when a bad installation if iTunes or QuickTime has corrupted or removed certain entries in the system registry.
iTunes and QuickTime are both pieces of software you are likely to install on your computer at some time or another, but can also be problematic if an update fails and corrupts registry entries or associated files. Uninstalling and reinstalling iTunes also sometimes doesn't completely solve the problem, and although the software may appear to work correctly, Windows Error 127 will persist.
You may see one of these messages after installing iTunes or running an update on iTunes to the latest version:
This is a common error message you may see after iTunes has failed or aborted an installation. You may also see references to "corefoundation.dll" and a number of other DLL files that are installed or updated during the iTunes installation process.
The reason these messages are displayed is because Apple Application Support, a feature of Apple software, has become damaged or corrupt. It's also possible that some DLL files associated with Apple Application Support have also been damaged. Because this service is common to many Apple products including iTunes, QuickTime, Mobile Me, and other related software, uninstalling one program and reinstalling may not fix the issue.
In order to solve Windows Error 127, you may need to uninstall all software by Apple.
The best way to do this is by going to add/remove programs from the control panel. Choose the first Apple product on the list and uninstall it. If you're prompted to reboot your computer, you can safely not do so at this point. Now, find the next Apple product on your program list and uninstall this also. Repeat this process until all Apple products are uninstalled. This may be a laborious process, but is unfortunately necessary in order to repair Apple Application Support. Once all Apple products are uninstalled, reboot your computer.
After rebooting, it may be a good idea to run a virus check, anti-malware check and a Windows stability check, as this will clear up any bad registry entries that may be calling DLL files that were uninstalled along with the Apple software.
You will also need to check and verify that the following folders have been removed:
If any of these folders still exist, delete them along with their contents.
Once this process is complete, you can now download and install the latest version of iTunes. Install it in the usual way and then check to make sure you can run the software normally. You can then proceed to download any other Apple software you use and install that too.