Running Disk Defragmenter has freed up over 30GB of free space!

I am not in the habit of running Windows Disk Defragmenter very often, but over the last few weeks I have been going through the process of importing my very large cd collection on to iTunes. My "C" Drive has a capacity of 222GB and I was down to 9.68GB of free space. I ran WDD but after 18 hours it had still not finished! I therefore decided to cancel the defrag, and after checking the capacity of my "C" drive, I found to my amazement that I now had 42.8GB of free space! I then downloaded the free Auslogics DiskDefrag and ran that. It completed in a few minutes and showed that the Windows Defrag had done most of the work but for some reason had failed to finish. Does anyone know why?

I have decided to disabled Windows Defrag and will use Auslogics version in future, as it gives information regards the progress of the defrag, and seems to be far more efficient and quick.

However, I am very surprised by the amount of free space that the defrag process has freed up. I have searched on various pc forums, and other posters have said the complete opposite to my own experience. The common consensus seems to be that defraging reduces the amount of free space on a disk rather than increase it!

There also seems to be a difference of opinion about how much free space one should leave on a hard disc to enable the pc to run efficiently. I was down to just over 4% before I defragged, but I have seen posts advising that one should leave betweeen 10% and up to 50% (which seems to me to be ridiculous!)

I would be grateful for any assistance that anyone can give me, in particular, why the defrag freed up (in my instance) so much free space.

I have not yet had any replies to my post so I thought I would add some further information. Before running Windows defrag' I performed a disc cleanup. This did not clear many files as I regularly use [COLOR=blue!important]CCleaner[/COLOR] to clear my temporary files, internet history and cookies etc. However, I am careful never to use the Registry part of CCleaner as I have been advised before not to use it.

Someone on another forum suggested that the increase in free space I experienced could be due to the fact that, because I had so little free space left on my hard drive before I commenced the defrag, the Windows defrag unintentionally caused restore points to be deleted. Do you think this is the likely cause for my dramatic increase in free space?



Why does Windows require a certain percentage of free space to function? And, does the amount of free space required vary depending on what version of the operating system one is running? For example, does Windows 8 require the same percentage of free space as Vista?