The new drive is named E when looking from the original C, right? You can
not have two C drives so the OS assigned drive letter to it. You probably
have another drive or partition named D. Since you say you cloned the
original to new drive then the new drive has all references pointing to it's
self and it thinks it is C. You can not assign the new drive letter to it
from within Windows and this is probably what you tried to do. Simply having
this new drive seen by the bios as boot drive will be sufficient to make it
be seen as C and once Windows loads from this drive it will then see your
old drive as different drive letter.
Best way to test this is by unplugging the old drive from the cable. If then
you see some error message that you can not boot on this drive, you may have
to run the Installation Windows CD repair portion in order to make the
Master Boot record work correctly and this takes only couple of seconds.
Depending on the cloning program you used, this should have been done
automatically by it.