Defrag your computer

I have found that after some use of your computer it seems to run slower.
And a friend of mine who has since left town gave me this piece of knowledge.
He told me that at least once a month you should defragment your computer.
As this places files back to where they should be and all the files that yoiu have moved to your recycle bin.
So I just thought I would let you on to this littel piece of information.
And just to add to this I was also told to do it a couple of times in a row as it helps to.
This is how I do it I defrag my computer twice and it does help.