Microsoft Office OneNote 2007 automatically creates backup copies of your notes at intervals you can customize. You can restore notebook sections or entire notebooks by using these backup files.
For each section that you restore, OneNote creates a new section in your current notebook with the name Section Name (On Date), where Section Name is the name of the original section and Date is the date the section was last saved.
On the File menu, click Open Backup.
In the Open Backup dialog box, in the Backup folder, double-click the notebook folder that contains the file or files that you want to restore.
Select one or more backup files to restore, and then click Open.
Tip: To select more than one file at a time, hold down CTRL and click each file that you want.