Sandisk Format

Question

Hi

Im using a sandisk 4gb sdhc card in my Canon A640 digital camera. Recently I tried to use the card to store some video for playback on a PC. I put the card in a USB card reader and tried to put the video on the card. I get a message saying that the card has not been formatted , would I like to format it? When I press the "yes" button I then get another message saying that there isnt a disk in "F" drive, please insert disk and try again.

I would be very happy if you can come up with a solution.

Thanks in advance

Dean