+1 ko ani ^_^, simple to use and actually free!
ok, some basics with file deletion stuff...
An HDD is similar to a physical folder with plenty of pages, most folders have TOC (table of contents) in the front. this TOC represents some of the sorts of pointer of the actual data and the pages are the actual data itself. Normally, when you delete file(s)/folder(s), what IS deleted is only the "TOC" and not the actual data.
Now, what these file scavengers do is actually read 'all' the 'data area', if the data is not overwritten by any other file (then lucky), if it is overwritten in some extent, then
TIPS:
when you accidentally delete an 'IMPORTANT' file, its best for you to do is 'nothing' on the drive where the deletion took place and make sure you don't do any "WRITE" activities to it and do the file recovery software(s) ASAP. if incase na-corrupt gyud ang hdd/flashdrive then need to format..., i-format lang with quick format, then do the software recovery as quick format only deletes the TOC and not the actual data ^_^. and make sure when you recover files, its much better you save the 'recovered' file in a different medium and not on the deleted medium (kay if same source kay na-a chance ang uban nga files kay ma overwritten nasab!)
if you get this, then good, if not, research more and I'm not a good person explaining things.
hope it helps a bit....