Lets say you need a free office suit, that can write documents and spreadsheets (and other things also) as an alternative to MS office. Then you could install LibreOffice, which is a multi-platform office suit. You can install it on Microsoft Windows, Mac OS X Tiger or newer, and Gnu/Linux operating systems based on the 2.6.18 or newer kernel. You can save your documents in .doc, .docx, .pdf and in .odf format. The latter is also the standard format in which the word files are saved. The programs included are:
Writer is the word processor, similar to Microsoft Word. You could use it to make a memo, or write a book with it. It is simple to use but has many nice features in my opinion.
Calc is the spreadsheet program, tha is similar to Excel. Calculate your budget or manage data. Rich in features.
Impress is the presentation program, like MS Powerpoint. Make a nice presentation with 2D or 3D clipart, and convince people with it.
Draw is an”All-Purpose Diagramming and Charting Tool” as described in their website.
Base is a database tool, similar to MS Access.
Math is the formula editor in Libre Office.
I myself use Writer and Calc and am very happy with those applications. The best part is that the software is Free/Open source software (it is licensed under the LGPLv3 license). It means that the users has the freedom to do whatever the users like with the software including sharing it with friend. Or sell it. As long as you give every end-user the rights you were given.
Give it a go, and you maybe will like it. If you do not like it, then just to uninstall it. Piece a cake.