The oldest rule of medicine is “first do no harm.” It’s much the same with computers. Today I’ll tiptoe close to that line.

Many times a computer is so fouled up, a person has to do one of three things: (1) Take it to the shop, (2) Dedicate weeks to trying one thing and then another or (3) take some chances with potent cures.

I think of these potent cures as desperate measures. I present them with no warranty, no promises. In fact, I suggest you only use them when no other option presents itself.

We’ll start with the least desperate of the bunch -- reformating the hard disk and reinstalling Windows. Some experts recommend this process fairly routinely, even for computers that are working. The theory is that you should start fresh once a year or so, removing any conflicts as well as hidden viruses or spyware. I don’t go that far. I only use this tactic when I can’t quite figure out what’s wrong with a computer but am fairly sure the problem is in the software, not the hardware.

If you do it, remember to back up all your data first. Also, make sure you have original disks for the programs you use.

The sequence at that point is: install the operating system; then the programs; then the backed up data.

My next tip is more dangerous. There are times when it will work, you’ll have to decide if you want to take the chance.

Remember floppy disks? Many people still send e-mail to me explaining that some important bit of information is stored on one. But the disk isn’t readable.

One desperate measure is to take the floppy disk apart. Carefully remove the inner circle of plastic coated with magnetic material. Then open a second identical brand new floppy and insert the inner material that you just removed. Put the disk back together. If it works — and it often will — immediately copy the material you need to the hard disk. Keep in mind that if you fail you’re ruined any chance of recovering the data.

Now lets turn to hard disks. When one goes bad, it can take much of your precious data with it — especially if you have not backed it up.

You can easily locate a disk recovery company by typing “disk recovery” into Google. I can’t recommend a specific service since I’ve never used one. But there’s a desperate measure that can help.

If the disk damage is not mechanical — and is software instead — there are programs that sometimes can recover your data. This is relatively safe and does not destroy the data if you fail. I’ll mention a couple of places to find these programs: http://www.runtime.org/data-recovery-software.htm and http://www.recoverdatasoftware.com/. I’m not recommending these programs, just offering examples. You can do a Web search using the terms: data recovery software.

In the worst case, the problem is mechanical. Software usually won’t help here. You’ll often recognize a mechanical problem by clicking or chattering sounds.

This is the point where only a commercial data recovery firm can help. There are some tricks floating around the Web that offer do-it-yourself remedies. I do not recommend them since, if they fail (and they usually do) you lose everything. I’ll tell you about a couple in case you decide to throw care to the wind with an otherwise useless hard disk.

The first one involves freezing the disk. Remove it, put it in a freezer bag and seal. Put that bag in a second bag, squeeze to remove the air, then put the whole shebang in the freezer for several hours.

When you take it out, let the the hard disk return to room temperature. Then reinstall it. If it works, immediately copy the information. Here’s why it might work: contraction from the cold, followed by expansion during the warm-up, can free balky parts.

Another trick that has worked for me is to remove the bad hard disk and tap it two or three times on a hard surface. I do not mean banging it like you’re driving a nail. Tap it.

I was serious in suggesting that you not try the last two tips unless the data on your disk is totally unimportant and you just feel like trying a parlor trick. Why mention them at all? I wanted you to know about them in case you stumble across a glowing review on the Web suggesting them.

Enough desperation for one day. I truly hope you never need to try any of these tips.