I would like to use guide below or in case OneNote is corrupted by unknown reason to use helpful topics below
OneNote Repair Toolbox
To recover your information from a section file backup in OneNote 2007, follow these steps:
1. On the File menu, click Open Backup.
2. Select the information section to open, and then click Open.
3. Click and hold the section tab, and then drag the section to an existing notebook.
Note Backup copies of notebooks are located in the following folder in Windows Vista: