File extension .MSO

As the name can indicate, the file extension mso is a file created when saving a Microsoft Office document as a Web page, contains information about objects included in the original file and will certainly be unreadable since the contents are encoded.
The file extension mso is used for sending Microsoft Word documents via email.
Most likely the Oledata.mso file will appear as a separate attachment on PC if you do not install Microsoft Outlook 2000 or later versions.
It contains information of the attachment to be rendered within the e-mail message.
A big number of conflicts in the file extension mso (and with a lot of other file extensions) are registry failures.
So cleaning the Windows registry may fix many of your errors in MSO file formats.
In order to do so, you have to run a complete scan of your registry looking for errors.