Hardware is a common cause of data problems. Power can fail, electronics age, add-in boards can be installed wrong,
you can mistype, there are accidents of all kinds, a repair technician can actually cause problems, and magnets you don't know are there can damage disks.
Hardware problems are all too common. We all know that when a PC or disk gets old, it might start acting erratically and damage some data before it totally dies. Unfortunately, hardware errors frequently damage data on even young PCs and disks. Here are some examples.
Your PC is busy writing data to the disk and the lights go out! "Arghhhh!" Is everything OK? Maybe so, maybe not; it's vital to know for sure if anything was damaged.
Other power problems of a similar nature would include brownouts, voltage spikes, and frequency shifts. All can cause data problems, particularly if they occur when data is being written to disk (data in memory generally does not get corrupted by power problems; it just gets erased if the problems are serious enough).
It's not magic; as computers age they tend to fail more often. Electronic components are stressed over time as they heat up and cool down. Mechanical components simply wear out. Some of these failures will be dramatic; something will just stop working. Some, however, can be slow and not obvious. Regrettably, it's not a question of "if", but "when" in regard to equipment failure.
You can have hardware problems on a perfectly healthy PC if you have devices installed that do not properly share interrupts. This problem is getting more and more frequent as we see multiple adapters installed in a PC that use the same interrupt (IRQ). Sometimes problems are immediately obvious, other times they are subtle and depend upon certain events to happen at just the wrong time, then suddenly strange things happen! (Software can do this too!)
(Typos and "OOPS! I didn't mean to do that!")
These are an all too frequent cause of data corruption. This commonly happens when you are intending to delete or replace one file but actually get another. By using wild cards, you may experience a really "wild" time. "Hmmm I thought I deleted all the *.BAK files; but they're still here; something was deleted; what was it? Or was I in the other directory?" Of course if you're a programmer or if you use sophisticated tools like a sector editor, then your fingers can really get you into trouble!
Malicious or Careless Damage
Someone may accidentally or deliberately delete or change a file on your PC when you're not around. If you don't keep your PC locked in a safe, then this is a risk. Who knows what was changed or deleted? Wouldn't it be nice to know if anything changed over the weekend? Most of such damage is done unintentionally by someone you probably know. This person didn't mean to cause trouble; they simply didn't know what they were doing when they used your PC.
One major source for computer infections is the Customer Engineer (CE), or repairman. When a CE comes for a service call, they will almost always run a diagnostic program from diskette. It's very easy for these diskettes to become infected and spread the infection to your computer. Sales representatives showing demonstrations via floppy disks are also possibly spreading viruses. Always check your system after other people have placed their floppy disk into it. (Better yet, if you can, check their disk with up-to-date anti-virus software before anything is run.)
Computer data is generally stored as a series of magnetic changes on disks. While hard disks are generally safe from most magnetic threats because they are encased within the computer compartment, floppy disks are highly vulnerable to magnets. The obvious threat would be to post a floppy disk to the refrigerator with a magnet; but there are many other, more subtle, threats.
Bottom line: There are tools to assist in recovery from disk problems, but how do you know all the data is OK? These tools do not always recover good copies of the original files. Active action on your part before disaster strikes is your best defense.
Beware of hardware problems. They attack out of the blue and can seriously damage data. But, how do you know what's damaged unless you know what you had?
There are many different kinds of hardware threats to your data. Some include:
Accidental or deliberate damage
The Customer Engineer or friendly salesperson
Problems with magnets
Active action on your part can help you identify problems and, perhaps, head them off early.