We have an HP ProLiant 580 G5 running Windows 2008 x64 with Hyper-V. The server is a host for 7 Virtual Servers running combination of 2008 and 2003. Currently the server has an embedded P400 controller which came with the server when we purchased it; this controller has the following configurations: Raid 1 as C drive (OS) Raid 5 as D drive where virtual servers are located. I wanted to install additional drives on the servers so I installed a second P400 controller with (4) 300 GB Drives and rebooted the server. During reboot I went to RBSU and created logical drive for the hard drives connected to second P400 controller that I installed, next I saved settings and continued with rebooting the server. After I logged to the server I opened My Computer window and did not see new drives I added for second P400 controllers, I am only able to see C and D partition. I opened Server Manager>Storage> Disk Management and I got a popup screen with the following info: You must initialize a disk before logical disk management can access it. Select Disk: Disk 0 (check box here) Use the following partition style for the selected disks: MBR (Master Boot Record) or GPT (GUID Partition Table) I did not initialize the new disk yet since I am not sure if I setup the controller correctly or not. It seemed also that the second controller and drives attached to it are now listed as Disk 0 since I see the following new configuration: Disk 0 – unknown – 838 GB – Not Initialized – Unallocated Disk 1- Basic – 136 GB NTFS – C: - Healthy (System Boot, Active, Crash Dump, Primary Partition) Disk 2 – Basic – 546 GB NTFS – Healthy (Page File, Primary Partition) Before adding the second P400 controller I had the following disks under Server Manager>Storage> Disk Management: Disk 0 – C Drive - with Status as System Boot, Active, Crash Dump, Primary Partition Disk 1 – D Drive - with Status as Page File, Primary Partition In RBSU and under Boot Controller Order menu and I see the following: Ctrl 1: PCI Embedded HP Smart Array P400 Controller Ctrl 2: PCI Embedded HP Storage PCI IDE Controller Ctrl 3: PCI Slot 9 HP Smart Array P400 Controller I have tried to contact HP several times with no luck on resolving this issue of why the drives for second P400 controllers are showing as Disk 0 and not disk 3 or 4. The people at HP Support have indicated that this is an issue with Microsoft but I don't think the issue is related to the OS but could be wrong. Please advice and thanks in advance for your input. B