OST Files – The .ost (off-line storage table) files are used by the Microsoft Exchange Server program to store messages, calendar items and other data items on the server. These files enable offline availability of the data.
PST Files – The .pst (personal storage table) files on the other hand are used by Microsoft Outlook do handle the same job. The .pst outlook format files maintain the archived items of a mail server. Since neither of the two file formats are counted against the size of the mailbox, hence it is a good idea to convert your data and save them as .ost or .pst format files.
The primary need to convert an .ost file to a .pst file occurs when an account gets deleted from a mail server or if the server is not working for some reason. Although there are several suggested methods to do the above conversion, the effective and confirmed ones come with a price tag. So here are a few FREE methods to convert your .ost file to the .pst outlook format.
Converting OST to PST Format
The first method you can try is to import your .ost file in Microsoft Outlook. Then create a blank .pst file and copy the data from the .ost file into the blank file and save it.
There are a few .ost .pst converters available in the market but most of them are costly. One free program is the ost2pst (download) which can effectively convert the .ost files to .pst files. Just search for it in Google. There is one issue with this free program though. It cannot convert files which have been created in Outlook 2003 or higher. This is because Microsoft changed the base format of the two file systems. Hence converting .ost to .pst is quite difficult in these situations.
An experimental method to convert .ost files of Outlook 2003 into .pst files is to trick the computer into thinking that it is an Outlook 2002 file and then convert it using ost2pst converter. First rename the desired .ost file (suppose abc.ost) to abc.pst. Use the scanpst.exe program provided with Outlook 2002 to scan this new .pst file. After the scanning is complete change back the name to abc.ost. Then use the ost2pst software to convert this .ost file to a .pst file. Since Outlook 2003 is backwards compatible, it should not have any trouble in reading the .pst file.
Remember that the above methods are experimental in nature and may not always provide with desired results. It is a good idea to back up your files before indulging in these processes!