sandisk?

I previously bought a 2.0 Sandisk sd card from Amazon.com for my Kodak Z710 7.1 megapixels camera. After taking a total of 72 still photos and 12 videos, the memory card shows that it is full. Why is that? I thought there will be more memory. Considering i have Filemate 2gb sd card and i get almost 600 pictures in 7.1mp and even more if i select 6.3mp, 5.0mp, 3.1mp or 1.9mp and 80 minutes of continuous video recording. But not with the 2.0 Sandisk sd card. Is there a way to get more memory without losing my pictures and videos that i have saved on the sd card? Or did i purchase and receive a bad sd card? Please assist. 1/25/08 12:51AM CST.