Secure erase

Is s/e the same as resetting my 520 480 gig to factory
defaults? Also when I try to s/e the boot drive in the toolbox it says that I
can’t perform this action on the windows drive. Will formatting the drive from
the win 7 install disk provide the same as s/e? What is the recommended method
of reinstalling win 7, secure erase or just format from the install disk like
an old style HDD?