I’m not really sure what happened, but this morning, one of my pst-files was missing and for another I got the error;

Errors have been detected in the file <path to pst-file>.

When trying to scan it with the Inbox Repair Tool (scanpst.exe), I got the error;

The file <path to pst-file> is not an Outlook data file (.pst).

When trying to start Outlook now, I get the error;

Cannot start Microsoft Office Outlook. Cannot open the Outlook window. The set of folders cannot be opened.

What should I do now to start Outlook and to get my data back?