That smell could be dust on something inside that's heating up when the machine is powered on.  I've noticed a definite musty smell on some of the machines I've picked up where they looked fine from the outside but when opened they were caked in dust (that's when I got in the habit of opening the machines before powering them on).

As to the drive size, if you open up the hard drive to browse for files and use the icon view it should show total size at the top of the window.