We had some Dell Optiplex GX270 computers donated to us, and the IDE hard drives were removed for security purposes. We installed new Seagate 160 GB SATA hard drives for use in our project, with new SATA data cables, and also a SATA power cable adapter. When we power up the computer the diagnostic lights on the back of the computer A-D are showing 3 green lights and 1 yellow, immediately followed by two beeps. This is happening on all six of the computers. According to the manual for the computer the lights indicate, "other failure has occurred, causes, ensure cables are properly connected to the system board from the hard drive, CD drive, and DVD". "Check the computer message that appears on the monitor" We checked all the connections as the manual states. Also we get no indication on the monitors because there appears to be no communication going to them from the computers. What else could be the problem.