My company has requested that I prepare several machines to be de-commissioned and I need to make sure all data is off these machines.

If the machines are being de-commissioned it is imperative that the data be securely wiped form the drive. There are software tools designed to do exactly that.

Active@ Killdisk is a tool that will overwrite every sector on the drive several times to ensure even the best data recovery labs could not restore a single file from the computer.

Use this tool to securely erase your computers before decommision.