I have an Alienware Area-51 M7700 / Clevo D900T. This was the most powerful desktop replacement on the market when it came out. If all the hardware is maxed out, it's still decent, and better than a lot of laptops out today...but it won't compete with the newer Clevo's. The hardware is simply too antiquated. But currently, it still serves a lot of purposes. It's a solid laptop.
The common assumption from people not familiar with this specific hardware is that the motherboard is damaged. Although this can sometimes be true, it is often NOT the case with the Clevo D900T.
Your problem is actually a common one. When installing a Windows operating system such as WINXP+, you MUST either slipstream SATA378 drivers into your Windows installation, OR have the drivers on a floppy disc (so you must also have a floppy drive). Otherwise the Windows installation WILL NOT recognize the hard drives. I've done this countless times now, and the SATA378 drivers must be installed for the Windows installation to recognize the hard drives. For some reason these drivers were never included in the Windows OEM installation discs.
If you don't slipstream the drivers, you must use a floppy drive, CD/DVD won't work for the drivers installation other than slipstreaming into the installation. Then when you are installing the O/S, it will ask you if you want to install Third Party hard drive drivers...hit the appropriate key for yes, then it will take you to a screen to choose the SATA378 drivers.
Be aware that you can't leave the machine unattended, as it only flashes the request for the Third Party hard drive drivers for a few seconds. If you miss it, or don't hit the "Yes" key in time, you have to reboot and start over.
Also, prior to installation, boot into your BIOS, and ensure the drives are set to "ATA" and not RAID, if you are not installing dual drives in a raid configuration...otherwise you WILL get hard drive errors when trying to boot.
You can find the SATA378 drivers by googling for D900T SATA378 drivers. Good luck.