Vista - disk space eater mr. defraggo

lol, i was just wondering why defragging my computer consumes approx. 10GB of hard disk space? and if there is anything i can do to regain that space, or prevent it from happening in the future. i have tried the disk cleanup function which helpfully regained nearly 60GB of system restore files during an unrelated loss of disk space, but disk cleanup did not work for me this time after defragging.

anyone have any ideas? i'm sort of new to computing and still in the frustration stages or learning, lol. thanks for any reply.

Defragment needs extra disk space to store intermediate files. this is like the situation u change your furniture's position. The 10GB space should be given back after the defraging is completed.

ok, thanks, I didn't know thats how it worked, but unfortunately my disk space wasn't returned, haha. I have only defragged my computer twice since I have had it, and both times noticed a large loss of space.
As of this message the defrag has been finished for nearly 24 hrs and my 10GB is still missing.

I have no idea what is going on!

Vista uses an improved version of NTFS. generally you don't really need to defrag it so often. Little performance boost you can obtain.

What software did you use to defrag? Is Volume Shadow Copy Service enabled on the drive that you defragged? That could be one possible reason. I am not 100% sure, but I've read that non-VSS defrag on a VSS enabled volume can cause fluctuations in disk space consumption. Another possible reason could be that a system restore point and/or shadow copies of files were created just after/before the defrag.

In Vista Home Premium, I defrag my drive using the VSS-compatible defrag mode of Diskeeper 2008 and I've never noticed any change in the disk space used. It's a great defragger with both VSS and non-VSS modes.

Thanks for that benjamin, but i unfortunately don't know what you are really on about! lol.
i used the defragger that comes with windows, i haven't obtained a defragging program from anywhere else.
Volume shadow copy service, i have never heard of, haha,but i'll look into it and see what settings are set.
I'm assuming vss being enabled creates a copy of some hard-disk info for the defrag process, which results in the observed loss of space.
if this is the case do you know how to correct that? is it similar to clearing the shadow files of sytem restore?

thanks for your help, sorry for my ignorance, lol.