Firstly, read the wiki. There's a lot of good information as to how you can go about doing it.
Secondly, before attempting anything, especially when it comes to Windows, you need to audit what disks you have on the machine and how they are set up. If the disks are mirrored in some way then you need to break that mirror so it all boots off one disk or a set of independent disks.
Your sole objective in all of this is to get an image from the original machine, make sure it has the right hardware support to boot into a KVM environment, boot it in KVM and watch it boot successfully. If you can do that then you've got a chance. ;-)