Windows guest has an HP recovery partition.
libguestfs confuses the HP recovery partition with an ordinary Windows partition, so thinks the guest is dual-boot. Various virt tools including virt-v2v and virt-p2v refuse to deal with multi-boot guests, so they wouldn't work.
libguestfs now recognizes the special HP recovery partition.
libguestfs, virt tools, virt-v2v, and virt-p2v can now be used on these guests.