Darik's Boot and Nuke, or "DBAN," allows your computer to load from a CD (the "boot") and then erases your hard drive (the "nuke"). Unlike the Windows Recycling Bin or some other programs, this will wipe your hard drive completely clean, securely removing all traces of software and files. This is obviously a last resort for when you or your company needs a fresh start. It is simple to burn it to a CD, which you must do in order to use it.
Download DBAN. It will download as an ISO file (a type of disc image). Do not open the file after it downloads.
Insert a blank CD-R into your CD burner.
Open "My Computer" and double-click the CD icon. Move the window that opens over to one side of your screen.
Drag the DBAN ISO file into the window that you just opened. Do not drag anything else into the window.
Click "Burn Disc" and confirm that you want to burn it.
Eject the disc. Restart the computer with the disc inserted to run DBAN.
Warning
DBAN begins running automatically when you turn on your computer with the CD inserted. After you hit the power button, it's too late to change your mind.