Microsoft Word Documents
Before saving a new Microsoft Word document (versions 2007 or 2010), ensure the file type is "Microsoft Word 2003 (.doc). You can find this option by clicking on File > Save As. Under File type, pick the one with the extension .doc.
On existing Word documents, you may need to click on "Other Formats" after clicking the File > Save As.. option, then select the type with .doc extention.