zeroing all data - keeping all apps

Hello all,
I have yet another puzzle. Hope you can help. I would like to zero all my data from my computer as I am selling it, but would like to keep all the apps I currently have including mcrsft package (The only disks I have at the moment are the ones that came with the MacBook). How do this to make sure the data is almost impossible to be retrieved? Your help will be very much appreciated. Thanks!

You can't zero out all your data and keep applications at the same time. If you secure erase the hard drive, everything will be wiped out and you'll be left with a blank hard drive.

Here's a better way:

See the following link = How to prep your Mac for resale.

Wonderful. Thanks so much. An the new used can have access to the applications on the computer, correct?