my external hard drive is not showing on my computer?

i have a 320gb external hard drive and i can’t see it on my computer (i’m using windows vista). I’ve tried the solutions posted here like the disk management but my drive is not displayed there.but as i explored the computer management box, i clicked the device manager button just above the disk management button it displays the disk drives available and it displayed my drive, when i right clicked the fujitsu the side box displayed the options update driver, uninstall, scan for hardware changes and properties only. i’ve tried to reinstall my hard drive but it does not change anything.i’ve tried other hard drive and my usb ports are working well.please help me i’ve got lots of files in the drive.help me please.thank you