Howdy, I'm running Windows 7-64 on a Optiplex. When I try to install a second hard disk, the BIOS sees it, but nothing in windows can see it. It does not appear in Device Manager, in Disk Management, or in Computer. I then discovered that in the BIOS, SATA was configured to RAID (even though, at that point I had only one disk installed.) I was told to set the SATA configurtion to ATA to allow Windows to see the second disk. But, when I set the SATA configuration to ATA, the system would not boot, and Windows Repair failed... So, if I set the SATA configuration to RAID, the system boots, but Windows can't see the second disk, and if I set the SATA configuration to ATA (as I was told by Dell "Support" folks would allow Windows to see the second disk) the system will not boot. Might you suggest ways I can get off this merry-go-round? Many thanks, A.C.