If you want your Windows 2003 VHDs to migrate back and forth between Virtual PC, Virtual Server, and Hyper-V as easy as possible, make sure they are running the ACPI multi-cpu HAL.
Hyper-V installs this HAL into any VHD image you put the Integration Services (IS) on. IS is vastly different than Virtual PC addition – think of them as native synthetic drivers and not emulations. You have to uninstall Virtual PC additions before you can install the Integration Services.
Breakdown by OS (so far that I have discovered):
Windows 2000 – do the same as 2003, but it seems more resilient to going back and forth due to a lack of native Integration Services (so far).
Windows XP – do the same as 2003.
Windows 2008 – it has Hyper-V support natively.
Windows Vista SP1 – I think you can hijack it and get the Windows 2008 IS pieces to work – haven’t tried yet.
For Linux, go to Microsoft's Connect site and download the Integration Services for Linux – so far, only Novell/Suse is supported but I am sure if you roll your own kernel, you can hack the patches in yourself (haven’t tried yet).
Some of this information I originally stumbled upon here.
Source:→ Aaron Tiensivu Blog
Microsoft, WS2008, Windows Server 2008, Hyper-V, Virtualization, Virtual Machine, Virtual Server, Virtual PC, Windows Server 2000, Windows XP, Windows Vista, Linux, Novell, Suse, VHDs, Windows OS