It has to do with your jumpers or cord placement.
Pull out the book for your motherboard, and see what it says about cables.

For example, mine has a blue port on the motherboard and a gray IDE cable. Whichever you wish to have as your primary master (Drive C) must be in the blue IDE port and on the first link in the IDE cable. And then the jumper must be set to Master.

i dont have a book for my motherboard
my motherboard = VIA P4VXMS Elite Motherboard
now when you say cables? what do you mean? the flat wide grey cables right?

Yes, I mean the thin and wide cables. Should have a red streak down one side, and you must have it on the correct side. Their should be some sort of indicator on the drive that shows thats where the streak gets placed.

okay...im pretty sure the ide cables are set correctly in place

now...how do i make my hard drive primary master.....and how do i set the jumper on my hard drive to master?

On the back of your hard drive, their is some little prongs and a crossover in one set that you might have to move.
http://www.wdc.com/en/library/eide/2579-001037.pdf
You have a WDC drive, so this sheet should be helpful to you.