Windows Live Mail – need to transfer emails from one computer (Win7) to another (Win8)

I have already setup WLM on the Win8 new puter. Old puter uses  WLM on Win7. I have transferred the contacts and thought I had transferred / exported the folders and their corresponding emails that are saved on the hard drive of the old puter.  But it didn't work.  There were a lot of the deleted / junk emails and many replicas but not the folders / emails I wanted to transfer.

I tried to export the folders / emails onto a SD card but  the wizard replies "The export directory must be ampty directory. Please select an empty directory and try again."

I even followed one of the answers to a post about this same thing....  copy and paste type of thing -- c:/users/login name/AppData/LocalMicro..WLM...

I am afraid to do that as (I am thinking) the data already downloaded to WLM on new puter will be overwritten....

It is a shame that I can't sync from old puter WLM to WLM  server than sync from server to new Win8 WLM....  that would be too easy....