I wonder if he replaced the correct drive but the new one comes up as a simple (standalone) drive with a lower ID. So when the computer tries to boot it sees the drives as [new drive as #1],[old drive in array as #2].
Then multi(0)disk(0)rdisk(0)partition(1)\WINDOWS will point to... the new drive... which has nothing on it -> boot fail.
So make sure that the correct drive has been replaced, add the new drive in the array, start a rebuild and then try to boot...