What kind of hash is it? Cain & Abel can crack the following types of hashes:
Radius Pre Shared-Key
which one of those (If any of those) do you want to crack or decrypt, NetTools by Relix has a very good file Decrypter...
Cain & Abel can even use Cryptanalysis Attack on some of those mentioned hashes, Brute Force on all. You can get Cain & Abel here: http://www.oxid.it
and it has a help file that tells you step by step how to use the software.