I was recently asked can we force our users to Save documents in Word 2003 format in Office 2007 ? and the answer is yes we can configure it using Office 2007 ADM files through Group Policies. Following are the detail steps.
1. Download the 2007 Office System Administrative Templates (ADM). Double click the file to extract all the *.adm files to a folder.
2. In the Group Policy window, right click "Administrative Templates" > choose "Add/Remove Templates" > click Add > locate the file word12.adm which you extracted > click OK, Close.
3. Go to the entry "User Configuration\Microsoft Office Word 2007\Save". In the right pane, double click "Save files in this format". Choose Enabled. In the field of "Save files in this format", choose "Word 97-2003 Documents (*.doc)", click OK.
I wanted to follow it up with few more details that the Save As list in File > Save As is not changed. If you are using the Save As list, please just click File > the right arrow of the Save As > Word 97-2003 format to save it.