Disk2Vhd is a realy nice tool if you are looking to migrate physical server to virtual. It’s a free tool from Microsoft. Can be download from below link
No need to install this tool. Just double click the exe and select the disks which you want to include.
This tool will take the snapshot of the system ( by using VSS) and create a VHD. We can import this VHD in to Hyper-V. Nice things is we could able to run this tool while system is in online.
Try it in Lab first then migrate production servers. We have done couple of servers migrated in to Hyper-V.