How about you check the dust shield on the back and make sure it isn't rubbing

 

if it is the rotors they are very easy to replace. and the pads are even easier. you would be amazed as long as you have the sockets and a jack. i did my rears in like one hour or maybe less. very satisfying work. good for people with little experience as well

 

yeah its pretty strait forward for most people....even easier if they got the Haynes or Chilton's to help guide em.

 

Let's do some checks real fast.
1) do the rotors have any scoring on them? Scoring is where the rotor is gouged, lightly or hard. These are very easy to see with the wheel on. Check the back of the rotor also, which can be checked by rubbing your finger on the rotor and starting from the center and working your way to the outer part of the rotor.
2) how old are the pads? That grind makes me think of the worn pad indicator, which is metal. Initially it will alert you by squealing when braking. If that is ignored, you get grinding...which is bad by the way. Did you hear this awhile back and just ignore it?
3) look at the outer pads and check for depth. You can do this with the wheels on. Use a flashlight and look at the pad.
4) the dust shield was mentioned, check that also. The only thing is, it won't make a grinding noise unless you have a good portion of the shield laying across the rotor...and, it will evetually be grinded down by the rotor and the grinding noise will eventually fade away. The dust shield will normally make a light grinding/squealling noise all the time and at any speed.
5) take the wheels off and look all over the hub for any possibilities. Note that there isn't much that can do this to begin with, but be thorough if the other suggestions above aren't it.