I installed two 1TB drives and set the dip switches to the setting for RAID 1, pressed the little button above them, but my PC was still seeing them as two drives. Next step,tried every combination of the dip switches all had the same effect. Then decided to set it as per the manual for RAID 1 and I pressed the little button this time with the drives switched on. Bingo! That did the job, Windows 7 asked me to format the drive, which was now showing as a single drive and the two lights on the unit were both on. I formatted "it" or "them" to NTFS using Disk Management, which took about 10 seconds. I started copying around 750 GB of photographs from another USB 3 external drive to this one, both connected directly to my PC's USB 3 terminals, I was a little disappointed at the transfer rate which was only around 50MB/s compared to around 30MB/s when using my USB 2 drives. I am using mostly Western Digital drives, but inside this enclosure I have one WD and one Hitachi drive. Because I was concerned about the speeds I dug deeper and found a good article that explains USB 3 in more detail.
One reviewer here had said that they found the dip switches were not as stated in the manual or the little picture on the back of the enclosure, my version is exactly as shown, so I can only assume that there are maybe quality control problems with some of these devices.