Based on experience with a lot of these, the two possibilities have been mentioned above - the drive may have failed mechanically or it may not be getting enough power. The symptoms are the same in both cases.

So try to fix the power problem first. Either a double headed USB cable or a separate power input might be required, depending on the brand. Try it on more than one laptop and be sure the USB port is powered (most are on recent machines, but three or four years ago, not all USB ports provided power)

Also, if the laptop is running on batteries, the power management system in most laptops can limit or shut off the power to the USB ports, so do a test with a fully charged laptop that is plugged in to the mains. You can also disable this power management function in control panel/system/hardware/device manager then go into properties for each USB root hub you see and choose the power tab.

If it's worth the trouble, you can buy a 3.5in to IDE or SATA adapter which would let you connect the drive to a desktop machine. If you need to get data off, or you need to be absolutely certain it is dead, this is a definitive test - but you need to get the drive out of the case, buy the adapter, open up your desktop and know enough about the insides to be able to make the connection. If the only copy of your important PowerPoint presentation is on an apparently dead drive, it can be worth trying.