Answers: Open Office:
http://www.openoffice.org/
Try the free, and M$-Office compatible, Open Office from:
Included: Writer (like Word), Calc (Excel), Impress (PowerPoint), Base (Access), Draw (M$-Paint) and Math
Just product sure that if you want others to know how to vista the documents using M$-Office Word, for example, accumulate them using "Save as..." in .doc format, instead of the evasion .odt format. Or use the built-in PDF creation side.