Ever since MS office 2007 was launched, there was not much of a file format change resulting a default file format compatibility between all versions of Office (98 / 2000 / XP / 2003).
The default extension for saving a file in MS office (98 / 2k / XP / 2k3) are same,
- .doc for office word
- .xls for office excel
- .ppt for office power point
Since Office 2007 is launched a new file format has been introduced which takes and extra 'x' in the extension. As for example,
- .docx for office word (2007 / 2010)
- .xlsx for office excel (2007 / 2010)
- .pptx for office power point (2007 / 2010)
