Find password to a word document
Complexity is (26)(maxPassLength).


You know that the password is only lower-case alpha characters?


  Would you recommend threading to reduce the search space?


It's possible that threads wouldn't help. The doc.open2000 will be more expensive than anything else, and your communication with Word may (I don't know) be effectively single-threaded (i.e. talking to a single Word process/task).

You might get better performance from a Word emulator which is designed to run on a server, e.g. from http://www.aspose.com/