Here's a little trick that I have been using since the old days...
Ever encounter a floppy disk that keeps giving you an error in the same sector no matter how many times you format it?
WE ALL HAVE!
The possible solution?
A COMPLETE ERASE.
Also known as Degaussing, it will permanently erase a disk and bring it to a state of no format.
Formatting a disk is an exact process depending on your PC but the end result is the same. The process of formatting will come across the same magnetic problem on the disk and will cause it to get an error in the same place or multiple places. It's caused by a slightly stronger or weaker magnetic field on several spots on the disk.
This is why you should never keep your disks inside your disk drives for too long, and why tape heads need to be demagnetized. When they are not, you will find that the tape head will erase the spot of music where the tape rests on the tape head.
The same goes for disk drives and floppies.
Degaussing will make all magnetism on the disk disappear, and ready to be formatted and be error free.
To do this:
Buy a RadioShack Bulk Tape Eraser.
There are two models, one for cassette tapes, and one for VHS tapes.
I suggest you get the one for cassette tapes since the one that erases VHS tapes cannot be held on for too long and will overheat easily.
The catalog number is 44-232.
Search on Ebay for "bulk tape eraser 44-232" and you'll see many matches. It's not hard to find.
To Degauss your floppy disk, hold it in your hand and turn on the tape eraser and make a circular motion for a few seconds, then while keeping it on, move the tape eraser away from the floppy and then turn it off.
Repeat this on the other side.
I prefer to do this twice on each side of the floppy disk.
This process works on both 3.5" and 5.25" disks.
If afterwards, you still get errors on your floppy disk, then I suggest you put your floppy through a really good and strong paper shredder certified for floppy disks, because at this point, NOTHING in the world can fix the disk.