The job failed with the following error: A failure occurred querying the Writer status." on the VSS Writer. We also run a daily system backup 1 hour after exchange job finishes - which runs sucessfully.

from:  https://www-secure.symantec.com/connect/forums/job-failed-following-error-failure-occurred-querying-writer-status-0

in the link above, I don't believe there was an answered.  seemed a little bit ambigious.  

one solution was to go to this link:  http://www.symantec.com/business/support/index?page=content&id=TECH179220

and to do:

Add the backup account in the following registry

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS\VssAccessControl

Ok, I can do that, but here's the question.  how do you add the backup account into the registry?  what value do I put in?