For me this is one of the scenarios where I'd want to use OVA export and import. Unfortunately a full bidirectional set of tests between oVirt, VMware, Xen Server or VirtualBox isn't within oVirt's release pipeline, so very little seems to work, not even within oVirt instances. I think I did get lucky with an oVirt import from a VMware OVA export once, the reverse already failed. Using the KVM/QEMU conversion tools should yield you COW disk images which you can upload to oVirt and then add to VMs you define as new. With a bit of luck and similar virtual hardware those could perhaps be made bootable. For Windows VMs this seems easier these days than with CentOS. Good luck and please report if you managed, otherwise perhaps redoing the VMs on oVirt (and potentially copying data/filesystems afterwards) may be easier.