For what it's worth, the "classic" way to deal with outlook .pst files
is (roughly, from memory):
Find an email provider that supports IMAP. IMAP is an email standard
where the messages are stored on the host computer, not stored on your
local PC. Many ISP's now support IMAP as well as POP.
Run outlook, connect to your email provider. Create an IMAP account in
outlook. Drag all the files you want converted to the IMAP folder. You
can create subfolders of that IMAP folder if you want to manage
things. This will transfer all your messages to the host computer.
Close outlook. Run thunderbird, or some other email client that
supports IMAP, but has a standard local file format such as mbox. Now
transfer all the files back down to your PC using thunderbird (or
whatever).
Mbox files are just text files, so you can search them, etc.
If you don't have access to an email provider that supports IMAP,
there are programs that you run on your PC that provide an email host,
and support IMAP, so you can do it all locally. This is more
complicated, and I haven't done it. A little googling should turn it
up, however.
This is a pain, but because Microsoft uses this proprietary format,
it's the only reliable way to do it that I know of.
Terry