I have a Canon PowerShot. I have a Canon PowerShot A620 camera with a memory card. Up until 1

Question

I have a Canon PowerShot A620 camera with a memory card. Up until 1 week ago the computer would read the memory card. I now put the card in and the green light is on but nothing happens on my desk top. My drive is not listed under devices with removable storages. What has happened. I want to be able to read the memory card.