I have seen the solved thread below and I did create a volume but still the tool cannot see the volume and it does not let me registere the hard disk:
http://forums.buffalotech.com/t5/Storage/iSCSI-might-not-be-registered/m-p/4998
I do have the latest version of the microsoft iscsi initiator: 2.08
I am using Windows XP.
I have created a volume using all 4 disks in a RAID 5 configuration (total volume size 2.771 GB)
First I tried without LVM.
Just enabled LVM and recreated it to see if it helps. At the moment it says "Checking RAID Array 1"
Ok, created 2 volumes (just in case). One for 1.9GB and one for 0.87GB
Still cannot register the volumes on the XP machine.
Tried and it registers ok on the Windows 7 machine ...