Thanks Allan. I installed version 9.6 of Intel® Rapid Storage and am almost more confused than before. The last 4 out of 10 power on boots were "degraded", then the raid array was rebuilt. (one of the boots Windows failed to start, but when normal windows start was selected from problem page, Windows came up OK, then raid array was rebuilt. When I can get to the Intel Rapid Storage display before the array starts rebuilding, the status of the bad drive is "missing". When I re-seat the plugs on the drive and poser up, raid array is rebuilt and all is OK until the next "Degraded" boot. I have tried re-seating the raid controller plugs into both drives and the mother board and have physically swapped the drive positions. For awhile, I suspected a problem with a specific drive serial number, because on the degraded boots, it did not show up in the raid array (during Windows boot process). After swapping the physical drive positions, now it looks like the other drive S/N might be the problem. Once the system is up and the Intel software shows rebuilding, I can not tell what drive is being rebuilt - they both show as OK. I could not find any logs or other status displays that showed which drive was being rebuilt.
Since I have never had any raid array problems until the string of disk failures started last October and I have now tried three versions of the raid software, I am starting to think that there might be some sort of problem with one of the drives I received from Western Digital under a warranty RMA. Do you think I should try to get another drive out of them under an RMA (hopefully) and replace one of the existing drives to see it the problem goes away?
Thanks for the help.