I am now using Windows Server 2008 as my primary laptop with Hyper-V (Link ) ... I now have a partial solution to this problem. You can have Hyper-V installed but not started by the following registry setting:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\hvboot]"Start"=dword:00000003

Now, when I start my laptop i have full access to the power management fucntionality. If I need to demo a VM, I can start Hyper-V with the command

net start hvboot

Power management is then disabled again until the next reboot.