If your system is not equipped with the PERC4 RAID controller and you need to add it, be careful when ordering from Dell's parts division.
Their suggested part number 340-9626 costs $999.00. It is my understanding this is an add on card with associated cables. Although this may function, it may not be necessary.
Part number 340-7478 costs $299.00. It is the key and memory required to utilize the embedded PERC4 controller on the motherboard you already have.
Here is a link to a helpful Dell forum.