Based on my experience, you must have the old HDD disconnected the first time you boot Windows after cloning.
It seems that Windows remembers volume letter assignments based on several different identifiers, but mainly the hardware ID (model/serial number).
If you boot with just the new disk connected, it'll see that the same partition is now on a different device and automatically update the volume assignments for the new hardware ID.
But if you boot with both disks connected, Windows will actually continue using the old disk because it finds an exact match for the old hardware ID it remembers. Even if you start the bootloader from the new disk, it'll still think that "C:" is on the old one.
I would suggest re-cloning the disk again (half a TB won't hurt an EVO), then immediately disconnecting the old disk before trying to boot Windows.
(It should be fine to connect the old disk later, even with its contents intact. It's of course okay to connect it after deleting the old Windows partition.)