Hello and thank you for your question, I look forward to assisting you today. Are you trying to open the pictures on your computer or through the camera?
Are you connecting the camera directly to the computer or just inserting the SD card?
The size you are using is just fine. I have the same camera and just started using a 32GB card. Try using VLC Media Player. It works on just about every type of media file and is much better than any of the included Microsoft programs.
Any luck with VLC?