I need a video adapter card for a hard disk drive.
i need a video adapter card for a Seagate ST3400620AS with 400 GB, 7200 RPM, 16 MB Cache, and a SATA 3.0Gb/s Interface. What is the best video adapter card for this hard disk drive?
You mean power adapter?
You can't need a video card for a hard drive. Maybe you mean you have the hard drive described, and need to know how to connect it to your machine and use it.
If your motherboard has SATA ports on it already, then you just mount the drive in your case physically and connect two things to it. One is a power supply from the PSU - the connector is usually black, and it must fit the connector on the drive. The other is a flat small cable that must plug into the data port on the back of the drive, and then at the other end into the motherboard's SATA port.
If your motherboard does not have SATA ports, you will need instead to buy and install a SATA controller card. I suspect this is your situation - the card you need is a SATA controller, not a video card. Check carefully which card type you get. Many now fit into the PCIe slot, but if you have an older motherboard without one of those, you need to get one for a plain PCI slot. That will give you the SATA ports to plug the drive into.
Read the documents for the SATA controller card carefully. Some may provide you with a disk of SATA drivers that must be installed in Windows so that it can use the new STA device. Others may do a trick many motherboard makers are using now - they have the SATA controller pretend that this new drive is a plain old IDE device that Windows knows all about and that eliminates the need for SATA driver installation.
Now also check whether your Power supply has wires coming out with a SATA connector on the end to supply the drive. If you have an older machine you may not have this. You may have only the older Molex connectors with 4 holes in the end, intended for power to IDE drives. In that case, buy a simple small adapter that converts this Molex connector into one or two SATA power connectors.
Once you can hook up your drive electrically, you still will need to Partition it and Format it before Windows can see it in My Computer and use it. If you're not familiar with those steps, search these forums for posts about installing a new drive. Or, go to your disk manufacturer's website and look there - they always have some instructions to help you start using their products. Often you can download and use utility software for this disk preparation task.