I have a built in RAID 1 system with 2 - 1 TB hardrives.  Within the first few weeks with the new system (computer is new also and custom built - Windows 7), I started getting a Raid controller warning box that reads, "There is at least one HDD unplugged.  It causes the raid damaged, or no HDD being detected on the controller.  The raid configurer will close." I got this message every couple of weeks, but now received it 2 days in a row.  If I restart, it does not come up a second time.
When the computer is booting up, I can see both 1TB drives listed as normal and the raid controller saying 1000 GB normal.  We opened the tower and looked at all the connections, which appear normal.
It has always appeared as one drive, being named "I" under "my computer", and I don't know of a way to see if everything is being mirrored or not.
Does anyone have any insight into this issue. A search in the forum came up with nothing similar.