[Fedora-xen] Xen error on FC 5, problem creating guest

Hi, I am working on a P4, 2.4 GHz intel system with 512 MB of RAM. I installed the xen0 and the xenU kernel that comes along with the installation DVD. I am able to boot xen, and the 'xm list' command shows the Domain-0 running. I tried to build a guest with the following config file kernel="/usr/lib/xen/boot/hvmloader" name="FC5Guest" memory=256 root="/dev/hda1" disk=['phy:/root/temp/disk.img,hda1,w'] vif=[''] saved to fc5-inst when i tried to create the guest using 'xm create -c fc5-inst' , i get the following error 'Error creating Domain: (22, 'Invalid Argument') ' I am new to xen, please help me out.