XP

So the default windows built in calculator doesn't give a damm about the standard rules. For example; 3 × 3 + 5 × 5 + 7 × 7 + 9 × 9 = 4,932

This can be fixed by switching to the scientific or programming calculator. The problem is that the default calculator just doesn't work like you'd assume and it can easily cause confusing mistakes.

The option to switch calculator types can also easily be overlooked for any first time users.