LibreOffice is a free substitute for Microsoft Office http://www.libreoffice.org/download/
It is a newer program based on OpenOffice which does still exist.
It is better than Office at opening a wide variety of files. For example I had a Microsoft Works spreadsheet that Office would not open but LibreOffice would. I could then save it as an Excel Spreadsheet. It will NOT open Microsoft Publisher. I recommend not using Publisher if you need to share the file with others or print it from other computers.
It includes, Writer (Word Substitute), Calc (Excel
substitute), Impress (Power Point substitute), and a number of programs I have
not used. A Visio compatible program is now available. This is a program
for drawing flow charts. See
https://www.youtube.com/watch?v=eyM5WoaYoUw for a tutorial. It
probably still has a substitute for Draw (a drawing program) Base (a data base program), Math (a program
to write complicated math equations).
It is very good at all kinds of file formats. For example I had a Microsoft Works spreadsheet that Office would not open but OpenOffice would and I assume LibreOffice would also. I could then save it as an Excel Spreadsheet.
If you open a file originally created with Microsoft Office, everything will go smoothly. If you originally crate the file with LibreOffice, it will default to saving it in its native format which can not be read by Microsoft Office. To avoid this problem either change the defaults is discussed above or, the first time you save the file, use "Save As" and specify that you want to save it in the Microsoft Office Format. Alternately you can set the default file format to what Office XL uses by following the steps outlined below.
You may want to only install some of the components to save space. For example I did not install the database component (Base) or their drawing component (Draw)
To set default file saving or “save as” format for new files in OpenOffice.org to be the same as Microsoft Office XP:
Rev 7/20/17 fixed