back to basics...

Hexadecimal or binary are just representations of the same information.

for more info on 2's complement, use google.
Search in "2's complement" yields as first entry:

http://www.evergreen.edu/biophysic...s_comp.htm

from that page,

Property
Two's complement representation allows the use of binary arithmetic operations on signed integers, yielding the correct 2's complement results.
Positive Numbers
Positive 2's complement numbers are represented as the simple binary.
Negative Numbers
Negative 2's complement numbers are represented as the binary number that when added to a positive number of the same magnitude equals zero.

Unless it's freezing when you did the test, I assume the positive numbers case applies to you....

regards