I recently had the need to look up the email address of an acquaintance that I misplaced years ago. During my time working with this person, I, thankfully, made routine backups of the local cache of my exchange server profile. I did this in case the server data happened to become corrupted or ruined since the local cache used by outlook is a full copy of the data stored by the server, given all content is set to be downloaded during a synchronization. Making the backup is typically as simple as copying the appropriate *.ost file from the “%USERPROFILE%\My Documents\Outlook Files\” folder (though, you should make sure to disconnect from the exchange server and completely close Outlook to unlock the file if it is in use or the primary profile).
Unfortunately, this file is not meant to be used as a backup, nor is Outlook capable of importing it. After about 20 minutes of Google-fu and failed solutions (usually meaning not freeware or simply useless advice), I came across this blog post describing two programs called Kernel PST Viewer (description, download) and Kernel OST Viewer (description, download). The second program caught my attention, and it turned out to be just what I needed. While it is somewhat functionally limited, it does exactly what it is expected to do and allows one to view the contents of an *.ost file in a simple and well organized layout.
I’ve been using this free tool called “Folder Size” (download available here) for a while now. It is a very impressive piece of (free) software that scans the entirety of a selected drive and produces an empirical picture of the distribution of occupied drive space. I have found this to be to be invaluable when cleaning out my disk space as it allows me to see the effective size of folders as well as files. The ability to natively view the size of a folder in explorer has been missing from MS Windows since its inception. Originally, I stumbled upon this application while attempting to address that specific concern, which it does. Beyond displaying the size of folders, it also shows the relative sizes of all items at the same branch of the drive hierarchy in both a percent column in the analysis results and a graphical display below as well as detailed file and folder attributes. Some of the options for the data displayed are type of visualization and default size basis (think KB, MB, GB, etc.). I highly recommend this software if you are going through the “where did all my disk space go?!?!?” routine.