Begin a found disk analysis by removing the disk from its paper sleeve if there is one, and eye-balling both sides for any distinct problems such as grooves, coffee stains or wrinkles. It is amazing what disasters disks can live through. During the early '80s when home computers first hit the mar-ketplace, there were warnings
everywhere: "Don't put disks by magnets, by your monitor, on your printer, or near your telephone. Don't bend disks, don't let your fingers stray from the label..." And on and on. Certainly you should treat disks carefully, but as we've learned since floppy drives became in-expensive enough for anyone to afford, disks just aren't as fragile as they were once thought to be. And certainly the plastic and Teflon they are made of are cheap enough to throw away, meaning dis-cards are common. So if you are rummaging through a company's trash bin and you see a man-gled disk, take it - you might be able to get some-thing interesting off it.
If there is nothing visibly wrong with the ( 5 1/4" ) disk, but you're still wary (because you found it in a garbage can or in a dusty place or something) you should carefully hold the envelope with one hand while rotating the disk with the other hand (using the hub ring). Look at the disk through the oval window as you do the rotation. Then turn the disk over and inspect the other side the same way. For 3 1/2" disks, you will have to hold open the sliding door with a finger as you rotate the disk using the hub ring.
If you suspect that a 5 1/4" disk is filthy, or if there is any dirt at all inside, rotating the disk may scratch it. Instead of rotating it, do this: Push the disk to the bottom of the envelope with your finger. Take a pair of sharp scissors or a knife and cut off a very thin strip of plastic from the top (label) edge of the envelope. With thumb and fingers, puff out the envelope, and ease out the disk. Don't wipe dirt off the disk - you don't want to scratch it. Try to blow away dust and dirt, or use a hair dryer set on low heat, or a can of compressed air.
Now look inside the plastic envelope. You will see a lining of a white gauze-like material. If that's dirty, throw away the envelope. Take a different disk ( that contains data you don't need any more ), slit the envelope open the same way, remove the disk and replace it with the other round floppy. Make sure the reinforced hub ring ( if it has one ) faces front. Now you can try using this disk on your cheap second-hand disk drive. For 31/2" disks, you can first carefully remove the door, then gently pry open the plastic envelope case with a knife. Don't jam the knife into the envelope; rather work around the edges and comers where the two halves are snapped together.
Re-move the floppy disk. Blow away any dirt, then put the disk into a clean envelope, using tape to keep the pieces together. Replace the sliding door if you can, but don't worry about that aspect if you have trouble doing so - most drives will not miss it.
51/4" disks sometimes get folded or bent. They are still usable but the bending can misalign your drive head. Not only will this ruin your disk drive, but subsequent disks inserted may be irreversibly damaged. Therefore, never use bent disks on a good drive, or good disks in your bad drive.
If you find a bent disk in the trash, first flatten it out as best you can. Put it on a hard, smooth, flat surface. Cover it with a few sheets of paper, then take a heavy book and press it down. Do NOT try to straighten disks by bending them the other way. If the outside envelope still seems in pretty bad shape, remove the inner disk and insert it in a good, flat envelope as described earlier.
Let's look at some of other ways a disk can be damaged but still remain salvageable.
