When i was taking pictures on my dslr with a sandisk 16gb sd card it only let me take a couple before it said memory full what can you do?

Thats odd- 16gb is plenty of room for all low and most higher end DSLR camera even shooting 'RAW' photos (no compression). For example, with a Canon 5D mrkII (over 20mp camera) I can take 400+ photos with highest quality settings before the card is full. Try importing all photos from the memory card onto your computer and then re format the 16gb card via your camera, this might solve the problem. If that doesn't work bring the card back where your brought it and exchange the card.