In the latest version of the Office Suite, MS Office 2007, Microsoft changed the default file format of its MS Word program from a doc format to the Open XML format called docx. Unfortunately, the docx format is not compatible with most common word processing programs including older versions of the suite. This means that a majority of users would have issues opening docx format files.
However, there are many free docx converters available that convert docx to doc. A search in any online search engine will reveal hundreds of results for such tools. It is important, however, that users are aware of the capabilities of the conversion tool that is used. Some tools allow docx format file to only be opened, but not edited. Others will allow users to open the docx format file in their existing word processing programs and then save it in an alternate format.
It is also important for users to study the documentation for the docx converter tool that is used to convert docx to doc. In most cases, such tools will usually convert the docx file into an alternate format that is generic enough to be opened by almost any word processing program. Examples of such formats can be the rtf format and the html format. This is important that the users realize some shortcomings of the html converter since html conversion will tend to lose some of the formatting of the original document. Bold, Italics and underlines will usually be supported in newer versions, but other formatting and special characters may not transfer over. The rtf format is a more versatile docx converter and will likely produce a document virtually identical to the original MS Office docx document.
One of the simplest and safest ways to deal with the issue is to use a converter that will categorically convert docx to doc. A trusted party for such software for Microsoft and Mac users to open the Docx format file is to download the MS Word viewer from the Microsoft website. This small program does not, however, allow users to edit the opened file. In case editing is required, the user can use the Open XML add on for older versions of MS Office.