In an ongoing efforts to increase the interoperability of its various technologies, Microsoft with Dialogika created a translator that converts the Microsoft Office binary file formats (.DOC, .XLS, and .PPT) into the Office Open XML standard format (.DOCX, .XLSX, .PPTX). A majority of the world’s documents are available in the binary Office formats and, for developers working with these formats (including .DOC, .PPT, and .XLS.), Microsoft published the specifications under the Open Specification Promise (OSP) in June 2008. A new version of the Binary to Open XML (B2X) Translator adds support for PowerPoint (.PPT) and Excel (.XLS) files.
More info: Binary to Open XML (B2X) Translator