Se non volete usare SysPrep potete sempre usare NewSid di Winternals... 
You might want to create a “base” virtual machine with the operating system and applications you want, 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.msdn.com/megand/articles/357570.aspx.
