My new mini sd card wont work.

Question

Hi. i have bought a kingston mini sd card and was using it fine. then after a few days it didnt want to work on the computer. it still works on my phone but when i plug it into the computer, nothing shows up. when i put my old mini sd card into the computer it works fine. i can plug my phone into the computer and go to the phone browser and then into the memory card but it is slow and i would rather plug the memory card into the computer and have the window pop up(auto-play). if anyone knows whats wrong, please help. thanks.