The only reason I get for having such a huge second partition is a tricky sd card. AFAIK, size of the sd card is written onto the sd card itself by the manufacturer. So you can make a 8G sd card and set its size to 24G
As for not being able to see the first one on windows, I don't know. Can you try with another sd card? An older one is better. A super new sd card may be unsupported by linux