Exchange 2007 CDO/MAPI is a cut-down version of MAPI. This works fine with Exchange Server Archiver (provided it's not one of the new evil versions of CDO), but it does not provide the functionality to read PST files. This is only available in fully-blown Outlook, so you must uninstall CDO, reboot, and install Outlook. This may require you to move PST Importer to another server if you've plopped PST Importer and ESA on the Exchange Server. If you depend on ESA being on Exchange (ie you don't use a CNAME alias), then you only need to install PST Importer on its' own server and point it at the ESA server in the options.