It is easy to copy files, but not in such a manner as to make the new drive boot up as the former one did. The Windows registry will not be identical and the new drive will not boot.
In the past, I have installed Windows on the new drive, and then transferred the files, but this is incomplete and unsatisfactory.
My current OS is Windows XP Pro, with service packs 1, 2 and 3 installed from the internet.