I guess there are many IT shops these days that migrate from VMware ESX or VMware Server to Microsoft’s Hyper-V. I believe this trend will continue as soon as Hyper-V 2 for Windows Server 2008 R2 is available. Unfortunately, VMware and Microsoft use different formats for their virtual disk images. VMware virtualization solutions use the Virtual Machine Disk Format (VMDK) and Microsoft uses the Virtual Hard Disk Format (VHD).
The free Vmdk2Vhd tool can help you convert a VHD image into VMDK format. Note that it is recommended to convert a big VMDK file to multiple 2GB VMDK spanned files first. Jérôme Laban has described some other issues you might encounter.
Converting the virtual disk alone is not the only problem you will face if you want to migrate virtual machines from a VMware ESX or VMware Server to Hyper-V. It is like moving a hard disk from one computer to another or using the same OS image on different hardware. Virtual machines are not that much different than physical computers. Thanks to Windows Vista’s and Server 2008’s new imaging capabilities, it should always be possible to move virtual machines from one virtualization environment to another.
It might also work with Windows Server 2003 and Windows XP, but I would recommend using a more professional tool to convert virtual machines with these operating systems. I have used Microsoft’s Virtual Machine Manager 2008 (VMM 2008) to convert VMware machines to Hyper-V and it has always worked reliably. VMM 2008 is not free, but you can download a 180-day trial. I suppose that’s enough time to convert all your VMware machines.
Have you migrated virtual machines from VMware to Hyper-V or Virtual Server? If so, it would be nice if you shared your experiences.