Dell XPS420 not reading secondary (Storage) hard drive

Hello all,

I purchased a Dell XPS420, and have been trying in vain to install a second hard drive into the system. The Hard drive works just fine in my older system. It's a SATA drive. I have switched the cables from my main hard drive, and the system is still reading the original hard drive, but not the new (storage) one. I have tried plugging in another hard drive just to see if it's the drive - but NADA. I enabled all the drives in the BIOS, I have plugged the SATA in all three slots in the Motherboard, no reading at all. DOes anyone have any solutions? The secondary storage hard drive works FINE in my old system - it's the Dell not reading it. Here is my system info:

2.40 gigahertz Intel Core2 Quad Q6600
64 kilobyte primary memory cache
4096 kilobyte secondary memory cache Board: Dell Inc. 0TP406
Serial Number: ..CN70821864H0EP.
Bus Clock: 1066 megahertz
BIOS: Dell Inc. A06 06/23/2008
Drives Memory Modules c,d
750.10 Gigabytes Usable Hard Drive Capacity
549.51 Gigabytes Hard Drive Free Space

TSSTcorp DVD+-RW TS-H653F [CD-ROM drive]

DELL USB HS-CF Card USB Device [Hard drive] -- drive 1
DELL USB HS-MS Card USB Device [Hard drive] -- drive 3
DELL USB HS-SD Card USB Device [Hard drive] -- drive 4
DELL USB HS-xD/SM USB Device [Hard drive] -- drive 2
ST3750630AS [Hard drive] (750.15 GB) -- drive 0

I called Dell Customer Support - he told me that I need two BLUE SATA cables, as I have a red one and a blue one. From what I have read, colour does not matter, it's the same cable. And, furthermore, the red & blue cables both work on the original hard drive.

Thank you!