Office 2007 changed the file extensions. In plain English this means that people with earlier versions of Microsoft Word, Excel, and PowerPoint loaded on their computers cannot view documents created with the latest version of this software. The people with Office 2007 could save the files in compatability mode. That would allow users with earlier versions to view the files. Sometimes Office 2007 users forget to do this. Sometimes downgrading causes the file to lose a feature. The link below if for a download from Microsoft that will help you view files created in Office 2007.