Here's a picture of the different memory cards:


XD is a type of memory card. Some other types are Compact Flash, SmartMedia, Memory Stick, MultiMediaCard and Secure Digital. You have to stick with XD cards but you don't have to stick to the brand. For example, when I got my Canon, it came with a 16mb Compact Flash Canon card. The camera can only use Compact Flash cards but whether it's a Canon brand card or not, it'll work just the same.

According to this place, a 64mb card should hold about 107 pictures at the highest setting. If you take the pictures at the lowest setting, you can get even more out of the card. On my card, I can get 868 pictures on the biggest resolution (1600x1200), 1389 at 1024x768 and 2719 at 640x480. So obviously, it would be nicer to get a bigger sized card but if you don't have a lot of space and need to take lots of pictures, the lowest setting will allow you to take more pictures.