Putting the old drive back in might not isolate the problem, but it's still worth trying. If the computer boots and runs normally with the old drive, that should prove that all other components are functioning properly, but that still won't help determine whether the new drive is faulty or there is a problem with the copy of Windows installed on it. If the old drive works it should narrow it down to one of those two problems, though.
If I had to guess, I would think it's an issue with the drive. If you can get to the BIOS, I would think that means your power supply, mobo, and processor are fine. It seems like it's hanging up right when the hard drive would first start being accessed to load Windows.
Can you hear the hard disk at all? Does it even sound like it's trying to do anything? Hopefully you don't hear the dreaded clicking noises.
I love Western Digital drives, but it's possible yours took a crap.