I need to erase all my data before giving out my old computer but I don't have the Windows CD.
How can I wipe my C: drive from the command line?
format c: /fs:NTFS /p:1
The format command used in this way will format the E drive with the NTFS file system and write zeros to every sector of the drive once.
A single pass of zeros to a hard drive will prevent all sofware based file recovery programs from extracting information from the drive. If you'd like to protect yourself from more invasive ways of recovering data, increase the number of passes or, better yet, choose a true data destruction program with more advanced options.
I recommend using DBAN (Darik's Boot and Nuke).
You can burn a CD from this download, boot to the CD and then erase the disk.
You can choose to reformat the partition before installing the new OS; this will by default erase the contents of the partition.
Alternatively, you can boot from a live Linux distribution (like Ubuntu) and run the GParted tool. It will give you a graphical representation of the drives on your computer and allow you to delete existing partitions and reformat them in a number of different ways, including FAT, FAT32 and NTFS.
You can also try KillDisk to permanently erase the contents of the partition/disk.