Going Though web doing a bit of research,The most recommended software seems to be for this requirement,DBX to PST Converter by SysInfoTools.A basic introduction from the official website as mentioned below.
SysInfoTools DBX to PST Converter is an advanced way to perform
conversion of multiple DBX files of Outlook Express into Outlook PST
format. It takes only one click and all the selected DBX files are
converted into PST format. If you are looking for a way to perform
batch conversion of DBX files, this would be the best option you can
This tool generates a new PST file in which all the selected DBX files are merged. The new converted PST file can be saved at user-defined location with a new name. It allows users to add new PST file to their Outlook profile. Users are also enabled to apply password on their new PST file for protection. This tool supports DBX files which are created in any version of Outlook Express and runs smoothly under all major Windows operating systems
Operating System: Windows 7, Windows Vista, Windows XP, Windows 2008, 2003, 2000, NT and 98.
Memory: Minimum 256 MB (512 MB recommended).
Disk Space: No temporary file is created.
To save converted output, make sure MS Outlook is installed on your system.
Free Demo Version Limitation
Demo version of the software contains all the functionalities. But there is only one limitation; software will convert only 25 emails per DBX file into PST file. Through this you wan check software capablity and its speed as well as accuracy but if you want to convert all emails of all DBX files then you need to buy the full version of the software.
Features of SysInfoTools DBX to PST Converter
Batch Conversion: It performs batch conversion of DBX files into PST
format at a time. Converting multiple DBX files into PST format one
by one is a tedious task to perform. You can select multiple files
simultaneously using this tool.
Password-protection: By using this tool, users can apply
password-protection to the new PST file (generated by the tool). You
can set any type of password (alphanumeric and multilingual) for the
PST file before starting the conversion process.
Search files: The search file option will allow user to search the
DBX files from the system automatically. This feature is useful when
a user does not know the exact location of the DBX files in the
Saves Output at Desired Location: The output, i.e. PST file, which is
generated after the conversion process of DBX files into PST format,
can be used at user-defined location with a new name.
Quick and Efficient: The conversion process of DBX files into PST
format is performed very quickly without taking much time. It does
not cause any changes or alteration to the original files. The
original DBX files are remained intact or unchanged.
Wide support and compatibility: The tool provides wide supports for
the DBX files which are created in any version of Outlook Express,
such as: 5.0, 5.01, 5.5 and 6.0. It is highly compatible with all
major versions of Windows operating systems.
Add PST to Outlook profile: The new PST file, which is generated by this tool, can easily be added to MS Outlook profile directly from here before starting the conversion process.
Easy-to-Use Application: This is an easy-to-use tool that requires no technical expertise. It works in a self-describing mode that enables non-technical users to perform DBX to PST conversion with ease.
Hope I have found the right solution for your problem!