Does the system POST? Have you connected the power cables to the SATA drives?
http://en.community.dell.com/cfs-file.ashx/__key/communityserver-discussions-components-files/3534/6560.sata_2D00_hard_2D00_drive_2D00_power_2D00_cable_2D00_connector.jpg
Power Cables:
- connect a SATA power cable from power supply to back of each drive.
Perfect Pict: (from alex...) http://img.tomshardware.com/us/2005/11/23/pc_interfaces_101/hdd_sata_connected2.jpg