Office Open XML (also informally known as OOXML or Microsoft Open XML (MOX)) is a zipped, XML-based file format developed by Microsoft for representing spreadsheets, charts, presentations and word processing documents. Under the General tab, towards the bottom you will see 'Unblock' button or checkbox next to 'Security: This file came from another computer and might be blocked to help protect this computer'. To unblock a file on Windows, right-click on the file and open 'Properties'. Please note you may need to unblock the Word files downloaded if your Microsoft Word software can't open them.