On the DriveImage XML page they write
Images are stored in XML files, allowing you to process them with 3rd party tools. Never again be stuck with a useless backup!
I can't help but imagine something like
<partition num="1">
<sector num="1">
<byte>0</byte>
<byte>0</byte>
<byte>0</byte>
...
</sector num="1">
...
...
This doesn't look too efficient, so I wonder what they do. I see no data format description there.