Question: I have winXP LibreOffice and MS office installed.

How do I make LibreOffice the default opening program for all of its know document types?
I know that I can change one extension at a time. But is there a way to change all of them?

I want LibreOffice to open .doc .xls and ... (I do not know all of them)

Answer: 
'Modify' worked for me. Thanks!

On Windows Vista:

* click START
* Settings
* Control Panel
* Programs
* Programs and Features
* Uninstall a Program
* Select the right program from the list
* click 'change'
* follow instructions.
To make office libre the default reader for all your documents:
Right click any document, tap Properties. A box opens that enables you to change the opener to office libre. Do this for a couple documents and OL magically becomes the default opener for all docs of the same type This works for windows 10 at least.