If your system contains a RAID, this is the RAID Controller warning you that the array is not complete.
If your RAID chassis levers are solid (with no perforated holes) the first thing to check is that all the drive bay LEDs/switches are illuminated below the RAID drive racks. If one of them is not lit up, push it in (to turn it on) with a paper clip or CD removal tool. Rough shipping can sometimes switch them off.
If all LEDs/switches are on, as the image above shows, continue with the following troubleshooting steps.
You'll need to get into the RAID controller to see the condition of the RAID (when prompted for a password it should be "secret" or "0000"). If you cannot get beyond the password prompt (perhaps somebody else changed it), the override password is "MNO974315743924".
ARECA RAID Card (systems after May, 2012)
1. Boot up and get into the RAID controller utility by hitting TAB or F6 when you see the 000/300 counting up.
2. Silence the alarm in Raid System Function/Mute the Alert Beeper.
3. Go to the Raid Set Function/Raid Set Information and select the RAID.
4. Notice what the Raid State is. If it says 4/5 this means it only sees 4 of the 5 drives in the array.
5. Taking some pictures of the View System Events pages may be helpful in determining the sequence of events leading to the problem.
6. Go to the Physical Drives/View Drive Information menu. Hopefully one of the drives is listed as FREE in the list. If this is the case you need to set this free drive as the Hot Spare. If you wish to attempt repairing the array, go to Raid Set Function/Create Hot Spare and select the drive that's FREE (hit ESCAPE to continue once it's selected). Choose "Dedicated to Raidset" and select the array with the missing drive when prompted.
7. If the drive is listed as Missing or Inaccessible in the Physical Drives/View Drive Information menu try and re-seat the drive which is represented by a Connector/Device Number both in the RAID utility and on the RAID drive levers. You can also try re-seating the data cables on the back of the RAID chassis, inside the case. If the drive is good it should show up in this menu after about 45-60 seconds (you may have to escape this menu and go back in to refresh the display). If it does show up as FREE, perform the Hot Spare assignment in step 6. If it still shows up as Missing or Inaccessible you could try removing the drive and plugging it into something like a write blocker to see if it's detectable. If the drive is undetectable by the write blocker you will need to open up a Support Ticket to determine warranty status for a replacement drive.
8. If you replace the drive yourself, replace it with the exact model, if possible. If one's not available select a drive (non Green) that is equivalent to, or has a greater capacity, than the original drive.
Under certain circumstances the "Raid State" under Raid Set Function/Raid Set Information may show as "Incomplete". This is telling you that the array has deactivated itself. The array will need to be reactivated before any changes (such as the Hot Spare Assignment) are applied. To do this go to Raid Set Function/Activate Raid Set and select the deactivated array. You should now be able to configure the array normally.
Adaptec RAID Card (systems before May, 2012)
1. Power on the system and get into the RAID utility (CTRL-A when prompted during system initialization).
2. Silence the alarm in the SerialSelect Utility/Controller Configuration/Alarm Control menu.
3. Check the array by going into the Array Configuration Utility/Manage Arrays menu.
4. Select the array and determine which drive is bad. It's possible the bad drive has a red light on the chassis, but is not always the case.
5. If a drive shows as FAILED, try re-seating it first. You can also try re-seating the data cables on the back of the RAID chassis, inside the case. If it is still not detected try connecting it to a write blocker as described in the section above. If the drive is undetectable by the write blocker you'll need to replace it with another equivalent or larger (non Green and SATA2 rated) HD.
If these steps don't help please forward us pictures of what you see when going through these steps.