yes but when i defrag my hard drive as you say to me its 1%fragment and i dergag it from lets say 3 it goes to 1 again why is it not goint to 0%???
Not all content can be defragged. Let's say you can swap two equal size chunks from between two files which were split, and simply restore both files to become contiguous. Easy peasy.
Now let's say you have less spare disk space, and one of the file fragments requires moving away content in excess to what is available...then there is nowhere to put the temp content and it can't be done.
Also, during the defrag, if a file is in use (meaning the file is "locked"), then that file cannot be manipulated.
There may be other files which are locked for other reasons as well, e.g., something due to the nature of the program or data associated with this (typically this would be related to a database). These too cannot be defragged until the lock is gone.
The closer your disk gets to full, then the more difficult it becomes to defrag.
There are a lot of services running, and sometimes services to preload something for performance gains at startup speed. These are candidates for being locked and no ability to defrag. If your game or other program has anything running related to it upon startup of the system, then odds go up you won't be able to defrag that particular content. If you played the game or ran the associated program once before defragging, then this too increases the odds you can't defrag that content simply because some process still exists in the background.
Note also that sometimes a program accesses a series of files during start, e.g., game assets. If the individual files are not fragmented, but the order of calling up those assets requires seeking back and forth, then defrag won't help because the individual files are already not fragmented. Possibly uninstalling that program, defragging, and then reinstalling that program would change the actual physical location on the disk of those files and then this would no longer be an issue.
One reason why the order of files might change even though the individual files are not fragmented would be due to applying patches. Patches do not care about disk drivers and filesystem drivers. Unfortunately, those drivers also don't care if the dozen or so updated files remain in the same order or not. If there was no space between those patched files, and the file size has grown, then you are S.O.L., and order must be changed.
Keep in mind the head seek you are hearing is associated with one program, and all of the other defrag can be completed, but if that one does not defrag, then you will still hear that noise because the head will still have to make that pattern of seeks upon start of your program.
FYI, 1% fragmented is actually a lot. Not in terms of performance, but most of the time I've had no issue reaching 0% fragmented even on moderately full disks.
Mechanical hard drive head seek is one of the limitations and reasons why many people like solid state...there is no defrag operation on solid state drives. Defrag of an SSD neither makes sense, nor provides any benefit (and is actually a danger to wear leveling).
When a mechanical hard disk does begin failing it may have some backup sectors, and you may get S.M.A.R.T. drive warnings of failure, and then the head will gradually start doing more and more seeks as block get marked bad (but this isn't something I'd expect just because you hear head seeks). See:
https://en.wikipedia.org/wiki/S.M.A.R.T.