Recently I dropped my backup laptop while my external HDD was attached via usb cord. The laptop was fine, but the HDD seems to have been incorrectly disconnected and now is no longer functional.

I have been trying to problem solve this on Windows and been getting further than on Linux, so I will report discoveries on both systems.

On linux, the drive is simply not recognized at all. It doesn't populate in the file system. I haven't got further than that. However, I know it's plugged in, as the tiny light goes on and the disk starts spinning, so there isn't a connectivity or port problem.

On windows, plugging it in nearly crashes the explorer! It takes forever to attempt to read the drive, but eventually I get a message that says either "the drive needs to be formatted before using it" or "device inaccessible; the parameter is incorrect." I attempted to use a data recovery tool to recover the files, even though they weren't actually deleted. After setting a program called Recuva to sense non-deleted files for recovery, it gave an error message that the file system could not be detected. To fix this, I was directed to reformat the disk (as windows had previously suggested) but the native windows disk format tool said the format could not be completed. I don't know why.

So I can't detect the drive, and if I can detect it, options to recover the files fail because the it can't be formatted and the file system is corrupted. It's a vicious cycle. I will probably try a different disk formatting tool on Windows, but I can use gparted to format the disk if I can get it recognized by linux. A recommendation for a file recovery tool for linux would also be much appreciated.

The HDD is a seagate 2 TB model-something-or-other

There are three parts to the drive i.e. the USB -> SATA bridge, the drives electronics board and the actual physical disk. If the drive is not recognized at all via the lsblk command or dmesg output then probably the connector on the drive is broken, maybe one of the data lines since you can feel the drive spinning.

Typically the USB -> SATA bridge is soldered directly to the electronics board these days so it isn't as simple as removing the drive from the case and plugging it in to another USB adapter. If the drive is recognized via dmesg the laptop is communicating with the USB bridge but not the electronics or maybe if the drive was still powered the heads crashed or maybe just jarred so they do not move correctly anymore.

I would guess if Windows takes a long time but then suggests the drive needs formatting then either the heads crashed or the USB -> SATA bridge broke at the electronics board. Without more information I would guess there isn't anything you can do from an operating system standpoint.

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If the external HDD fell too then it could be any number of physical damage, head crashes, etc. that have happened.

You could try opening it up and trying the drive itself in a separate caddy and pull the data off it that way.

If that's successful there are a few replacement enclosures around. I recently re-cased an old 2.5" spinner that was in a USB2 case in to a USB3.0 enclosure.

That is one way, but only would work if the drive is a standard sata interface. If it has the soldered in USB-SATA interface then doing the replacement to a different caddy would likely not work.

If the drive is not working then no harm in trying anything.

Indeed, but if the drive is dead anyway there's no harm in opening the case for a look.

Formatting the disk effectively removes any options to recover files. One of the expensive data recovery services might be able to get some files after formatting, but formatting is basically antithetical to file recovery. Your problem seems to be about basic access, as already noted. With any luck, the drive can be removed from its USB case and connected directly via SATA port to find it accessible. Likely the fall irreparably damaged it mechanically.

I did not realize that. I'm not sure how that's much different... isn't data recovery a read of faded magnetic imprints on disks? Why is deletion different than formatting?

I formatted it using diskpart on windows. A data recovery program was able to recover a few jpgs but nothing that I wanted. Wow that sucks.

When a file is deleted only metadata that points to the file is deleted not the actual data unless you a specific utility to erase it. Formatting a filesystem does the same thing, it initializes all the metadata to zero but does not actually erase or zero the rest of the partition unless specifically done by another utility. Depending on the filesystem some data at the beginning of the partition may be overwritten. Basically data recovery programs scrub the disk looking for specific signatures to find files on the disk.

There are utilities that are able to recover some (possibly fragmented) of the data from a disk that has had the metadata wiped. Ddrescue is one of those that may assist.

Using windows to format a disk that was previously linux makes things even more problematic.

The thing to remember going forward is that you should NEVER use utilities that write to the disk until AFTER the recovery has been attempted & completed so that you avoid causing more issues.