Windows Image Backup and also disk2vhd ( http://technet.microsoft.com/en-us/sysinternals/ee656415 )

I love the VHD format!

Also wim is a nice choice (created by the imagex.exe in the Windows Preinstall Environment based AIK toolkit, also used by Vista and Win7 setup): Not block level based, but contains all ACLs etc. needed to deploy an image