My Passport essentials 500 gb external hard drive does not show up in computer

My external hard drive initially worked the first time i connected to my laptop which works on windows 7, and I copied most of my data into the hard drive, but later when i reconnect it does not show up in any other computer or laptop. I am worried  if i would lose all my data, i tried all methods by checking in device manager or disk management the hard drive is not visible and all the time a white light seems to appear the moment hard drive is connected to laptop. Please help me its urgent and im needy

Hi, be sure to use the USB cable that came with the passport and avoid using extension USB cables or USB hubs. You can also try connecting the passport to another PC.