access from other computers

I have installed Security Update 819696 and the DirectX
9.0b End-User Runtime and now this computer is not
accessible (was accessible pre-install) from other
computers even though the sharing options are set on both
the network properties and the hard-drive properties. I
have searched the knowledge base and have been unable to
locate any information about this problem or information
relating to this particular patch and what it does to the
system. Could anyone advise as to what has transpired with
my computer.