I have an external hard drive which worked fine and it is my backup harddrive. There are also some files on it that I would really want to keep. It's a 400GB Freecom drive in FAT32.

All of a sudden, after not using my HDD for a week or 6, a message pops up with: "You need to format your disk in drive X".

I tried a couple of solutions that I found, but they give different results:

* `sfc /scannow` in the command line tells me that everything is fine. All drives work great.
* I checked 'Disk Management' and deleted the hard drive letter and added it to another one. Didn't help.
* I checked the hard drive on another PC, same message.
* I did a Deep Search in [Recuva](http://www.piriform.com/recuva). It only returned 50 mb of files.
* I ran an analyse in [TestDisk](http://www.cgsecurity.org/wiki/TestDisk_Step_By_Step). It returned that there are no partitions found on the hard drive. 'Disk Management' does say that there is one primary partition.

Did I do something to my HDD in the meantime? No, it was just laying in a clean drawer. Could somebody please tell me what is wrong with my external HDD?