Sysprepping virtual machines
You might want to create a “base” virtual machine with an operating system and applications, and then copy its .vhd file to use for other virtual machines. Before you make copies of the .vhd, however, it’s important to run Sysprep in the guest operating system. This way, the first time you start a virtual machine that uses a copy of the base virtual machine’s .vhd file, the guest operating system will be assigned a new SID and other identifiers, so you won’t end up with network conflicts between different virtual machines that use the same copied .vhd file.
Read all about it in the article I just posted in the "Deployment" category at http://blogs.technet.com/megand/articles/357570.aspx.
Please note that Microsoft does not support using a tool other than Sysprep for cloning virtual machines. For more information, see this Knowledge Base article: http://support.microsoft.com/Default.aspx?id=162001.