Flash drive not working

Hello Everyone

I have a very serious problem with flash drive(usb). It was working properly on my Pc but when i copied some folder in it, and removed it. Then i plugged it in again, but it does seem to working. when i plugged it in, the only drive appears on the computer, when i click it, it seems to empty. but when i check the properties it is used. the data is there but does not appear. Kindly help me.....