If you need to prevent date and time synchronization between a Virtual PC 2007 virtual machine and its host machine, look at this post for the necessary steps but if you need to achieve the same result with a Windows Virtual PC virtual machine, you can do so by adding the following line to the vmc file for your virtual machine:

<preferences>
 <hardware>
  <bios>
   ....
   ....
   <time_sync_at_boot type="boolean">false</time_sync_at_boot>
   ....  
   ....
  </bios>
 </hardware>
</preferences>

You can achieve the above by also running the following visual basic script:

'Title: Script to disable timesync for a VM.

'Usage: cscript ScriptName <vmname>
Set objVPC = CreateObject("VirtualPC.Application")

'Get virtual machine name from command-line parameter
Set objVM = objVPC.FindVirtualMachine(WScript.Arguments(0))

'Disable TimeSync During Boot Time
errReturn = objVM.SetConfigurationValue("hardware/bios/time_sync_at_boot", false)

'Get object for GuestOS
Set objGuestOS = objVM.GuestOS

'Disable TimeSync During VM Execution
objGuestOS.IsHostTimeSyncEnabled = false


Copy the above in a file with the vbs extension and run it from a command-line prompt with the following instruction:

cscript MyScript.vbs "MyVirtualMachineName"

where MyScript.vbs is the name of your script file and MyVirtualMachineName is the name of your WMV virtual machine.