A defragger does not delete files - if there are more files each time it's down to natural causes not the defragger.
File fragmentation is where a file is split up and each part put on a different part of the disk - it makes disk operations very inefficient and can slow down the machine.
Defragmentation just tidies things up - brings the fragments together and makes the file whole and in one place.
You might consider some system housekeeping to remove the dross - CCleaner is quite good and it's free.
Wikipedia has a list of Defragmentation Software that you might consider - also an article on defragentation.
Good luck...
W Gates
October 2014