I doubt if files/data on the PC are completely deleted/erased. All bits of these files/data would have to be set to Hex "0" or "1" and that may take all long time to do.
I will always remember the practise of "Pre-Allocating" space on the Mainframe at the beginning of a job so the space would be there at the moment when actually needed. Thus grab 500 Cylinders of free space and catalogue them as a single file. Sometimes I took a peek what the contents was. And yes for sure, there would be Payroll or other sensitive data displayed. Until I reported this to the System Guys, then they put a patch into the "Pre-Allocation" to actually "Clear" the contents.
As far as I know, Data in the Recycle Bin is NOT deleted/erased, just the Pointers to that Data have been removed and it becomes "Free" space. To show that, an actual coredump of "Free" space should be done.
Broni is correct!