This is another document describing how to setup SSO with Openfire and Spark with Windows 7 and Server 2008 R2 by Jonathan Murch.
He has posted it on one of the threads. I haven't seen it posted as a document yet, so this way it will be easier to find it.
I think it is a bit better structured and has more details than Speedy's guide. Maybe someone will find this one easier to follow.