Linda -
My fav utility site - used 'em for over a decade now ...
www.nirsoft.com
You can try this for pst file recovery (password on the PST file - not the e-mail acct password )
PstPassword - http://www.nirsoft.net/utils/pst_password.html
There are SEVERAL 'pst recovery' programs on the net - I don't see any of those at nirsoft, however. Haven't tried any of the other off-brands/commercial ones - so can't give you guidance there.
Hopefully - it was simply encryption that rendered your PST file 'unusable' - rather than other corruption problems.
Here is a sample of one of the pst products that comes up from 'google ad search results' when the search is started from nirsoft's site.
Sponsored Results
Outlook PST Recovery
Recover Lost or Deleted PST Files. Follow the Simple Instructions!
http://outlook-pst-recovery.pchelpsoft.com/
Like I said - haven't checked it out, haven't used it - can't recommend it or warn against it.
IOTW: CAVEAT EMPTOR - except for actual nirsoft utilities. I do vouch for them.

Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good ...