So. Yeah. That started to happen. It was just fine until I lend it to my brother, he just tried to connect it to his PC (I was watching) and then, bam, stopped working and a message for me to format the PC appeared. That HD has my entire life, and while I have a back up for 95% of the stuff, I really don't want to lose that 5%.

 

Assuming you have tried different usb ports, a basic but often overlooked troubleshooting step, try changing the drive letter of the external. If that doesn't work, try another external enclosure, I've had problems with cheap enclosures before and buying another has solved my issues.

Outside of that there is recovery software out there, but I have zero experience with those so can't recommend anything. If that 5% is really that critical I'd get a professional to do it if that is possible for you.

 

Something similar happened to me once - turns out that the partition table got wiped out. It was a simple, if sweat-inducing fix, but I don't remember what software I've used to do it any longer. Might want to google around and give it a shot, although the probability that it happened to you as well is low.

Is that device even visible if you run diskmgmt? (Win+r -> diskmgmt.msc)

As for recovery software I've had decent success with EASEUS Data Recovery. It's some strange chinese program with design straight out of 2006, but most of the time when the files were recoverable (didn't overwrite anything etc) recovery was successful, even with complete file tree. If file tree is lost, then you're most likely fucked - there's an option to recover all files, but it's not very helpful when there's 60k files that might or might not have proper names.
Oh, and as always - it was some time ago, so it's entirely possible that the program turned into ad-ridden POS. I think the version I used was 5.4 or 5.5, but YMMV. Google is your friend.

If you go with recovery - don't write ANYTHING to that drive. Just get a new one - you'll need it anyway if the old one gave out, even if you manage to get it working again. If you can't live without those files, get two new ones - clone the one that failed on the first, then do recovery onto the second one (then set up RAID, since hey, lotsa HDDs).

@edit - just in case, you do use 'safely remove hardware' when disconnecting hdds, right? I, uh, didn't know this thing existed for a whole lot longer that I should.

 

Also, if you haven't already, try a different USB cable.

 

Aye, you can just create an image of the drive. Use a linux distribution or powershell, so long as it plugs in you can make a copy, even if it needs formated. You can use http://dcfldd.sourceforge.net/ if you feel comfortable with using the command line. Or just pick a data recovery program from google. The one that blob mentioned works fine, just make sure to not let it install anything extra to your computer.