See the last non-spam\garbage posting here:
http://groups.google.com/group/xxclone/browse_thread/thread/d9066806b59eb2f1
Other software, Paragon comes to mind, is Windows 7 rated:
http://www.paragon-software.com/
For XP (NT), and I'd bet this carries forward into Vista and Windows
7, the OS installation is keyed to the physical disk (VolumeID\Disk
Signature). A Copy is converted into a Clone (Bootable Backup) by
Swapping the Drive Letter and Volume Label Assignments between the
Source and Destination "in the Registry of the Destination". This data
may be seen at HKLM\SYSTEM\MountedDevices\. All the necessary tools to
carry out this conversion (same as xxclone does) already exist in
Windows with no additional software or components required. More
detailed examples have been posted here several times and should be
searchable from keyword in this paragraph.
DES