VHD in Windows 7
Given changes to Windows backup formats in Vista/7/2008 the following tools may be rather useful as W7 and 2008 become ever more common:
this 2nd one can even allegedly be used [with care] with Vista native VHD backups. or
which allegedly also allows one to write to the VHD as well.
Alternatively, if you need quick access to VHD backups, you can mount them directly from the 7/2008 Disk Manager, but the mount doesn't survive a reboot.
Also VHDTool - command-line tool which provides useful VHD manipulation functions including instant creation of large fixed-size VHDs.