Visit Ost2pst download website and install the free version of Kernel for OST to PST to convert orphaned Exchange OST files to PST. After the recovery, one can preview the recovered emails and other items. But for saving them in PST, MSG, DBX or EML format in the required location, one needs the full version of the software. If you are happy with the preview, purchase the full version. Before downloading, check the installation requirements.