USB NOT recognised after working on it for a week

Please please please could someone help, i am born BC and have a terrible problem. I Have just down loaded all my pictures onto a SAMSUNG EXT harddrive. It has been working all week, and i took it off my laptop and plugged the usb into my office PC. Nothing happened the light came on but nothing registered, i could not even eject it. I unplugged it and tried to plug it into my laptop... well my world fell appart, I dont have any backups and I need help.
THe laptop says USB not recognized......please help I cannot afford to loose 10 months hard work