Erase unused space option


New Member
Hi there,

I am a newbie, so plz forgive my question to those of advanced level
My question has to do with the ''erase unused space'' option.
If I choose to ''erase unused spece''. will Eraser delete ALL my data in my hard drive, or would it delete any old files, fragments of files deleted in the past, that may take some place in my hard drive.

AS you can realise I am kind of hesitant using this option as I am afraid of my hard drive getting fully erased and that I will need to format it

Thank you in advance