My Win 7 does the same.
If I press 1000 * 10 % it displays 100.
If I then press = it displays 100000 which I don't understand. I think it's saying that 1000 times 10 percent of itself is 100000 which I suppose is OK, but it's counter-intuitive for me. I didn't expect the % sign to "execute".
it's obvious enough what it's done that it doesn't confuse, though.