i haven't understood what the real problem's cause is
I will try to give you an explanation of what is happening...
Operating Systems use a bitmap to keep track of the space in a volume (ie: hard drive partitions) that is being used, and what space is still available. This is called a volume bitmap.
If you ever ran the Windows95/98 defrag program and watched the details-it showed a window full of little squares being moved around-then you've seen a close representation of a volume bitmap. The little squares are the bits in the map.
So how does it get messed up?
Well, if your computer occasionally freezes/crashes then the open files on the hard drive don't get closed properly so there are errors and corrupted files. This includes the metafiles that keep track of your directory system. Usually, windows does a pretty good job of recovering from these small disasters. But if it freezes/crashes frequently then it causes so many problems that errors compound and cannot be fixed.
How to avoid it?
Fix the problem that creates the freezes/crashes. If it's a software program then get rid of it. If it's a piece of hardware then replace it. Not only does it cause problems for the file system, these freezes/crashes are hard on the computer itself and wear it down. If not fixed properly then it eventually will fail completely-which is much more expensive to fix.
There was a popular oil filter commercial in the 70's. The mechanic said 'you can pay me now or you can pay me later', referring to changing the oil filter when doing an oil change is cheaper/smarter than replacing the engine later because a dirty oil filter destroyed it.
Also do regular cleanups. Temporary internet files are clutter. Why make your computer keep track of 50 plus megs of files that likely won't be accessed ever again. Do a defrag every week. Don't ignore freezes/crashes, something caused it-try to find out what it was and fix it.
Hard drives use a volume bitmap to keep track of useable/bad sectors. When a bad sector is detected, the bit is marked as bad so it doesn't get used. Some drives have reserve sectors, so it can bring one of these into the map as a replacement. This bitmap can be corrupted and create problems. Get a diagnostics program from the manufacturers website to check a hard drive before using it.
It is a good practice to always run a diagnostics on a hard drive, even new ones, before putting it into use.