I've been running virtual machines on Hyper-V in the MTC lab with great success. The performance is excellent and much faster than it was on Virtual Server. One challenge though is that it would be nice to be able to start up a Hyper-V VM on my laptop. Occasionlly, I get calls from customers asking about a setting in the VM they used in the lab. This means I need to have a Windows Server 2008 x64 server lying around which isn't always the case. Naturally, I could install Windows Server 2008 x64 on my laptop and run in Hyper-V natively but this would require dual booting and re-partitioning the drive. Unfortunately, Virtual PC is not an option today because it doesn't support APIC or 64-bit VM's. So as a workaround I started looking at VirtualBox (http://www.virtualbox.org) which is free for personal use. It supports both 64-bit and APIC mode. Supposedly, it supports the VHD format natively but I could not get this to work (according to the VirtualBox forum this problem will be fixed in version 2.1). So until that version is released I have to convert the VHD to VMDK format using WinImage (you could also use VMWare Converter, but I didn't try that). It took about 1 hour for a 20GB disk image. You then need to create a new Virtual Machine and use the existing hard drive. If you want, you can also enable settings like USB 2.0 support as well as SATA. Once that was done I went into VirtualBox and booted the VM. After it booted, I then installed the Guest Additions. Note that as with going from Virtual Server to Hyper-V, you may also get prompted to reactivate Windows (happened to me on Windows Server 2003 but not Windows Server 2008. YMMV).