An Regain Software OST to PST converter is a software tool that allows you to convert Microsoft Outlook Offline Storage Table (OST) files to Personal Storage Table (PST) files. This conversion is typically necessary in situations where you need to recover emails, contacts, calendar items, and other data from a damaged or inaccessible OST file or when you want to migrate your Outlook data from one system to another. Here are some key features and steps you can expect from OST to PST converter software:

1. File Conversion: The primary function of OST to PST converter software is to convert OST files into PST format while preserving the email structure, attachments, and other data.
2. Selective Conversion: Many converters allow you to select specific folders or items within the OST file for conversion, giving you control over what data is included in the PST file.
3. Bulk Conversion: The software should support bulk conversion, allowing you to convert multiple OST files at once, which is useful for organizations or individuals dealing with a large amount of email data.
4. Preview: Some converters offer a preview feature that lets you view the contents of OST files before the conversion process. This helps ensure you are converting the correct data.
5. Maintaining Folder Hierarchy: A reliable OST to PST converter should maintain the folder structure during the conversion, ensuring that your emails are organized correctly in the PST file.
6. Preservation of Metadata: Important email metadata such as sender, recipient, date, and subject should be preserved in the PST file.
7. Attachment Handling: Attachments should be included in the PST file, and the software should handle them appropriately.
8. No Data Loss: The converter should ensure that there is no data loss during the conversion process.
9. User-Friendly Interface: A user-friendly interface is essential to make the conversion process straightforward, even for users who are not technically inclined.
10. Compatibility: Ensure that the software is compatible with your version of Microsoft Outlook and your Windows operating system.
11. Customer Support: Look for software that offers customer support or documentation to help you in case you encounter any issues during the conversion process.

Some popular Regain Software OST to PST converter tools as of my last knowledge update in September 2021 included Stellar Converter for OST, Kernel for OST to PST Converter, and SysTools OST to PST Converter. However, new software options may have emerged since then, so I recommend checking for the latest reviews and recommendations to find the most suitable OST to PST converter for your specific needs. Additionally, remember to back up your OST files before performing any conversion to safeguard your data.