As this is usually replied with spam conversions I have to declare this a link free discussion except for moderators.
Google your question topic and you find the usual but those that sell such never tell you unless they are honest that you do not get all that was on the Exhchange Server. There are spammers with conversion products that are not honest about this.
Beware those conversion products as not one can get what's not in the OST.
I need to convert an Outlook 2007 Professional .ost file to an Outlook 2007.pst format in order to move it onto my current computer. I no longer have access to the exchange server, and my contacts, as well as some necessary emails are in the .ost file.