If you want a totally free replacement for the Microsoft Office program suite, then I urge you to go to OpenOffice.org and download the program there.
Once you set it up, you might want to change the defaults to saving in Word and Excel formats. Nobody has to know you are cheap!
To change the defaults, in the program click "Tools", then "Options", then expand "Load/Save" and select "General". Then for "text documents" select Microsoft 97, and for "spreadsheets" select Excel 97.
OpenOffice is a very comprehensive program. If you want something more lightweight, which you can get into and out of quickly, try Google Docs.