[Fedora-xen] Vanishing Harddisk

Hello All, I hope some one can help me. I have xen running on Fedora Core 6, now when I try to add a guest os using virt-manager there are no hard disks detected. the whole process goes fine until I have to pick a partition for installation. I tried using both a file as avirtual disk and also a partition, in both cases I come to stop because no hard disks or partitions are selected. Ali