CCLeaner Drive Wiper

Yes, in simple terms free space is the unassigned areas of the disk. Keep in mind that nothing is "impossible" unless you melt the disk into a blob. I can't say why or how but rest assured, there's probably only a handful of people that can recover even 35 pass wipes. For most security needs, a three-pass wipe is sufficient.

But, be warned that if this is a Solid State Drive (SSD) you could dramatically shorten it's life and slow the drive down by repeated wipes.

I use Ccleaner free space wipe one pass. I have a ssd. If someone stole my desktop they would be the kind of person that wouldn't go through the time, money and trouble to see what is on free space. Free space is not empty. Things you delete go to free space waiting to be wrote over when the space is needed. The only reason I use the wipe is because sometimes I use my computer to test different malware ect. When a scan removes them they go to free space and I don't want them there or any place on my computer. Who knows but some nut made a virus to come back alive from free space and do its thing. I don't think it will wear out my ssd. My ssd is guaranteed for 5 years by Intel no matter how many reads/wright it does or does not have. I don't baby my ssd I just use it.
It doesn't seem to mind being used.

I'm sure somewhere, there is someone who would want it. In fact, I remember being told one time (no clue if the following is accurate) when the CIA, FBI, and other federal agencies dispose of a hard drive, they format at least 35 times, then shred it in to hundreds of little pieces (I assume they would use something akin to a wood chipper), then collect all of those pieces and melt them down.

A 3 pass overwrite used to be DoD standard but was found to be recoverable with some common methods so the 7 pass was developed. Peter Gutman developed the algorithmic 35 pass which is supposed to wipe the last trace of any data so it can't be recovered by any means including electron microscopic examination.

I have read even a single pass on a SSD makes the data completely non-recoverable since it is not stored on magnetic media like a HDD has.
http://en.wikipedia.org/wiki/Gutmann_method

HTG Explains: Why You Only Have to Wipe a Disk Once to Erase It

http://www.infosecisland.com/blogvie...Overwrite.html

The other passes (number of times) are older standards which really don't apply today. (In my understanding)

From Mr.Gutman himself : "In the time since this paper was published, some people have treated the 35-pass overwrite technique described in it more as a kind of voodoo incantation to banish evil spirits than the result of a technical analysis of drive encoding techniques. As a result, they advocate applying the voodoo to PRML and EPRML drives even though it will have no more effect than a simple scrubbing with random data. In fact performing the full 35-pass overwrite is pointless for any drive since it targets a blend of scenarios involving all types of (normally-used) encoding technology, which covers everything back to 30+-year-old MFM methods (if you don't understand that statement, re-read the paper). If you're using a drive which uses encoding technology X, you only need to perform the passes specific to X, and you never need to perform all 35 passes. For any modern PRML/EPRML drive, a few passes of random scrubbing is the best you can do. As the paper says, "A good scrubbing with random data will do about as well as can be expected". This was true in 1996, and is still true now."