External USB harddisk shows up as removable device after falling down

Seeing as this happened after it fell down, I'm guessing it's not something that has to do with the PC. Since the external drive is essentially a HDD and a case it's one or the other. If you have another external case you can place the HDD in there and find out for sure. I'm not sure what that would do to the warranty, if it still has one. Also be prepared for a lot of disassembling; external HDD cases that come complete with a HDD tend to be built like onions around the drive.