Before you can try any 3rd party paid tool for OST to PST conversion, you must try few easy manual tricks which are as effective as a professional converter tool. The manual tricks don't require any such paid software or any cost. I'm sharing a blog post here in which you can find detailed information about OST to PST conversion manually - wordpress.semnaitik.com/2013/10/29/convert-ost-to-pst/

If the manual tricks fail or don't work, then only you should try a professional tool. Generally manual tricks don't work with corrupt OST files. In such situation, you must try a tool that can support conversion of corrupt OST files as well. The OST Recovery software is the best solution one can have if he/she is having corrupt OST files. It first scans corrupt OST file, recovers data from it, and then saves them into a new PST file. You must download its demo version for free evaluation.

To know more about this software, you can visit: www.data-recovery-solutions.com/ost-recovery.html

Thanks.