Try to disable Windows Time service

>I have a situation where I need to "set backwards" the date and time in a Win7RC installation running under VPC 2007 for testing a client situation.
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>I've turned off all the auto-updating items I can find in both the interface and the Task Manager -- but now, when I manually change the date and time, it only holds those values for a few seconds and auto-updates again.
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>This is driving me *nuts* trying to figure out -- anybody out there got any ideas?