I Have purchased 4 different memory cards for my Pentax model istD camera, I keep getting a Memory Error with each card, the last card I purchased by going to the Pentax web page and purchased the so-called correct card, What can I do to make them usablr?

[spinno]

Make sure that the firmware is up to date.
My first guess is that the cards have too much memory for the camera. When the ist series was on the scene so to speak max card size was I believe 4 gb. Anything larger than that won't work.

[paulh]

Make sure that the firmware is up to date.
My first guess is that the cards have too much memory for the camera. When the ist series was on the scene so to speak max card size was I believe 4 gb. Anything larger than that won't work.

Yes - even with the latest firmware, the max card capacity is 4 gb.