Critical Onenote 2010 Files From Backup Unreadable!

Hi -
I have been using an Acer Aspire 340 to run WHS v1 since 2010, and do regular backups of all my systems, including an IBM Thinkpad I use for work. The Thinkpad crashed recently - hard disk is totally unreadable. I was able to recover most of my data from a USB backup drive, but it turns out that OneNote's Unfiled Notes, which are stored under Local Settings/Application Data, were available only from my WHS backup. (Actually, I had them on an online backup, but those were a few months out of date). I opened up several WHS backups for this laptop, and restored the Onenote files (*.one), which appeared to have been backed up. But when I try to open in Onenote, I get an error saying they aren't OneNote files and can't be read. The older versions restored from online (IDRIVE) read just fine.

I read that there had been earlier data corruption issues with WHS including One Note files, but those appear to have been resolved much earlier than I bought my system, and appear to have only applied to data stored on Shares, so I don't think that relates to my problem.

I have some really important notes I'm trying to recover - any thoughts would be appreciated!

Thanks,
Michael