CC will overwrite and permanently remove from prying eyes the data the file entry in the MFT is currently pointing to. It might, however, be possible to recover the data and the perhaps the entire file from other fragments left from previous edits, or in the page/hiber/sysrecovery/autobackup files, etc.
but I did not find the way to securely delete a single file[as example: from the desktop]
AIM TO "Winapp2.ini";
If I tell you it won't hidden/secret anymore!
No, nothing really, private mail things like that, it's just that I heard if you delete a file from "the Recycle Bin" it won't delete just change place(or something like that)
This has been discussed quite a bit before and the best is to use Eraser application for files but I believe that shredding things in an email client such as Outlook Express or Thunderbird is not possible as they use their own database files and getting in there to shred an individual item could be disastrous.
Sent the item to its Deleted Items Folder then empty that Folder then Compress the Folder and it will be gone.
I'm not sure about Thunderbird though as I do not use it.