I accidentally deleted more than 30 spreadsheet files by typing the command "del *.xls" when I meant to issue the command "del *chase*.xls". So I bought the latest version of a program named Recuva that I had used in the past to successfully recover accidentally deleted files, and when I ran it it stated that 30+ files had been recovered and none of them had been partially overwritten by another file. However all 30+ supposedly "recovered" files consist entirely of binary zeroes. Was this done by the delete command?