Instant Messaging hash values

["Nick Duda" <nduda () VistaPrint com>]

I'm looking to create a software restriction policy via GPO to prevent
different instant messenger services (AIM, MSN, Yahoo, Trillian..etc)
from running based on the hash value. Short of gathering all know
binaries for each client is there any way to obtain hash codes from past
versions anywhere....perhaps a website with a repository of hash values
for binaries?

Thanks in advance,

Nick Duda - Systems Administrator