When I want to write a report, I use Word 2007. But I'm sure there's some software which is specialised in writing reports, i.e. it'll make it easier and more professional to have a professional report, professional cover, Title page, Table of Contents, Abbreviations, glossary, Acknowledgements, Abstract (Summary or Executive Summary), Introduction, Body, Conclusion, Recommendations, Bibliography, Appendices, etc.
I also wish to save the the document as a .doc or a format which will be accurately converted to a .doc.
If your best suggestion is to use word, then go give some suggestions on how to have a professional report structure ready rather than me building one every time.