To export a folder or set of folders from Outlook 2010 you do the following:
1. Open Outlook and go to File -> Open -> Import
2. Choose ‘Export to a file’
3. Choose ‘Outlook data file (.pst)’
4. You will see the folderstructure of you Inbox, choose which folder(s) you wish to export and dont forget the option ‘Include subfolders’.
5. Give the location of where you want to save your Outlook data file. Dont overwrite any existing .pst files and give it a new name.
6. If disired choose a password and click ‘Ok’.
The export will now be started and you cant use Outlook during this process.