I'm trying to add two new hard drives to my Dell XPS Studio 9100, but Windows 7 will only recognize one of them at a time. The two new drives, as well as the original drive, are SATA 1TB Seagate Barracudas with identical specs. The BIOS recognizes all three drives and I do not have RAID enabled. However, Disk Management in Windows 7 only sees one of the drives, and only one of the drives is shown in Device Manager as well.
My original drive running the OS is in SATA port 1 and the two new drives are in SATA ports 2 and 3; SATA port 0 has a DVD drive connected to it. To debug the problem, I turned off the computer and physically disconnected the drive on port 3 then started the computer. I found the drive in port 2 in Disk Management and created a partition for the whole drive and set it as D after naming the volume BackupXPS9100. I could view and interact with the new disk in Explorer, and I created a file named This is disk 2.txt on it. Then I turned off the computer, physically disconnected the drive on port 2, reconnected the drive on port 3 and booted. Now the D drive was still accessible even though it was a different drive! Even the volume name was the same even though I had never named a volume on this disk. I created a file named This is disk 3.txt on this hard drive and then shut down the computer. I then disconnected 3, reconnected 2 and booted. Now drive D still exists and it shows the file This is disk 2.txt.
So, it seems like Windows can't tell the difference between the two drives. They are interchangeable when I connect one at a time, even though they are on different SATA ports. The problem is that the second one is not accessible when they are both connected. How can I fix this?