What Microsoft did was come up with a new format instead of the .doc at the end of the name, it now puts .docx. This adds some extra features to the document, but it is only readable to Word 2007, or you have to download a document converter so your older Office programs will work with the new files.
Microsoft Excel is also affected by this, instead of .xls as the extension, it is now .xlsx.
The biggest problem is when you create a document in this new format, and you send it to someone who does not have Office 2007 or the converter to read it. Also, PowerPoint has this feature, and the new file extension is .pptx.
There are a few ways to fix this.
1. Download the Compatibility Pack so you can read the newer 2007 files in older versions of Office.
Microsoft Office Compatibility Pack & Converter
2. Every time you save a document, change the "save as type" at the bottom to "Word 97-2003 Document (*.doc)"
3. Set the program default to always save it as the Word 97-2003 (.doc) version.
This is my favorite, and most people seem to like and use this feature.
Click on the Office button at the very top left of the page in MS Word or Excel and click on Word, Excel, or PowerPoint Options button, depending on which program you are using.
Click on SAVE on the left side menu
The top choice says "Save files in this format:" and in the box it says "Word Document (*.docx)"
Click the down arrow to the right of that and from the drop down menu choose "Word 97-2003 Document (*.doc)