Hi,
In my opinion, the best way to save/archive emails that are currently in an OST file is to create a new PST file and then copy (or move) the emails to the new PST file. In order to create a new PST file, you would first need to go to...
File > Account Settings > Account Settings > New.
The new PST file should then be listed under your OST file.
I hope this answers your question.
Thanks,
Jason Stone "The Computer Tutor"