aside from what eyal has said.
i've still got my 1998 win 98 eide orginal hd running and i am using it for only temp stuff because it did start to have bad sectors on it back in 99, so i added another hd. since then i have added 4 more in to the system.
only this last one i put in was the hd from the old win98 se computer that crapped out on me. as a matter of fact i believe the hd wiped and formated it's self when i was trying to fix it in the win98se system. i have been testing it in the jukebox of mine by running it only as an empty drive with a page file formated to ntsf.
the other week my jukebox refused to boot, this hd was clicking . so i unpluged the power and rebooted the computer its been going fine eversince the hd was unpluged so that is one bad hd with 6 op systems in 10 yrs.
not bad considering 15 more in the systems and one is a ata hd, and one is a win 7 laptop hd.
as to the drives going bad in different sectors yes it happens the disks in them are glass plated with magnetic material just like the tapes you buy are. and after a lot of use the material starts to flake off. but in computers here the software in win98 uses scandisk to do a surface scan and find the bad sectors puts a mark in front of the bad sector trys to get any data in the sector moved to a new one, and then marks the end of the bad sector. thus making the op system see that it can't use that part of the disk.
now with knowing that you will wonder what if they whole thing is going to go bad, you will see that in the number of bad sectors being increased and the need for doing scandisk every so many months to weeks to days.
if you keep getting more sectors each time you better get a new hard drive fast. in xp the scandisk was replaced in the op system by the checksum on reboot. that is what does the scanning for bad sectors there. i don't know what they are using in windows 7,
but with the lifespan of the hd's up to about 10 yrs or more now. that is little worry as you will more likely buy a new system in 7 years with a new op system. thus getting a new hd.
still there is also the natural world that messes with the hd. as with any electrical items. that is sun spots or solar flares, those can cause blackouts like the one a few years ago that shut down half the USA. and part of Canada. then there is the normal every day things that we can't even see that happen to bombard the hard drives, little nano particals of solar dust that are sent through everything at the speed of light. we cant feel it but it is like a rain shower to the magnetic field on the harddrives and you know what rain does to a sandcastle or to nicely freash painted houses.
that is what those particals do to the hd's. now it takes time and that is why the lifespan is at 10 or more yrs.
that was mentioned by eyal.
lots of stuff to get a geek scared but more then that. is the bugs. yes bugs. real life ugly looking bugs.
they were found to be eating plastic and glass about 7 years or so ago by a lab doing research on something else. they found scratches in their brand new petre dishs. but when they looked they were not scratches but tunnels in the dish. they were found with a super electron microscope one that could see nano sizes and smaller and that is what the bugs are in size nano parasites on bactriea that were in the dishs. to them the glass particles are like cracks in walls of the house so they go through them and make them wider apart,
then some one coming back from the equator jungles found their cdroms were destroyed by the same type of bugs that ate in them. so there are things that will destroy the data it just takes time.
only thing that seems to last the longest is man's memorys passed on from generation to generation. but even man can get brain worms so ?? if god wants it all gone he has a way to get it gone.