Why lost all notebooks after reinstall OneNote?

Question:
After reinstall Windows system and Office, run OneNote, and I cannot find all my notebooks. How can I recovery my notebooks?

Answer:
Not like Evernote, OneNote doesn't auto sync all notebooks after reinstall.
The reason is OneNote can save the notebooks in many location.
OneNote can save notebooks in

• OneDrive.com，
• Office 365 SharePoint Service,
• Cloud storage: Dropbox ...
• Local disk,
• LAN file server, NAS server,
• SharePoint server in LAN,
• U disk,

This is destined that OneNote can't open all your notebooks at once.

Solution:
The OneNote notebook file is designed as document file of MS Word. You need to find the notebook file by yourself, and using "Open" feature to open them.

So, you need to remember the location of your notebook saved (Maybe saved in OneDrive.com, Office 365 SharePoint Service, Cloud storage, local disk, LAN file server, or U disk). And open it.

There is an add-in "OneNote Gem - Favorites" can help you to group and remember the notebooks location.

Grouping OneNote Notebooks, Close or Open a Group of OneNote Notebooks.