Tutorials for teachers - Learning about software programs and how to install them?

While I was taking the computer training session for my co-teachers, I noticed that teachers are enthusiastic about use of computers and internet. During online search for education materials, we need to save our documents, but often it becomes difficult to open that file.
What kind of files we need to open?
Mostly these files are in Word, PDF, PowerPoint, Zip, Rar format. So if your computer doesn't have specific software to open these files, you cannot get results from your search. I am listing here essential software programs which are helpful to open specific kind of files.