I am having a similar issue with some differences. I needed to reformat my tablet pc hard drive. I was using an older version of Outlook - 2003, I think. I didn't 'export' to a pst file, it was already saving my email, calendar, etc, into a pst file. Instead, I copied that pst file to the hard drive of another computer. I had been having trouble with some sort of 'redundancy error', so it had a hard time copying the file, so I 'zipped it' down, and copied the zip file. Now, as I've extracted the zip file back to the pst and copied onto my newly formatted hard drive and my newly installed Outlook 2007, I get an error message that says the file is not a pst file. I've tried every way I can think of from 'importing' it, to adding it as a data file, and get the same message. Unfortunately, I'm an architect, not a tech, so I'm sure I've messed this all up somewhere, but all my emails and contacts are in this pst file, and if there is ANY way to get it restored, I really need to try. any help is appreciated.