How do you format a Windows computer and delete all data on the computer?

You use the “format” command with the security (overwrite) options. If necessary you can run it from your original install disk. Or you can delete your user data and then run disk defrag.

Go to My Computer. Right click on your harddrive. Click “format”.

take the HD out and replace it with a brand new one, set a magnet on the old one then toss it in a lake :)

I think it’s better to use the storage manager to delete the partition, make a new primary partition, and format it, but not with the “Quick Format” choice. Don’t assign a volume, don’t assign a path.

Please note: Everything on the disk will still be forensically available. If you have anything compromising on there, first use a diskwiping utility set to DOD standards, the follow the instructions above.

You can’t wipe out the drive while you are running Windows from the drive. So, two choices

1)
Put the drive in another machine as a 2nd drive, then format as others have said.

2)
Boot from a CD and wipe the hard drive, using a tool like Darik’s Boot And Nuke
http://www.dban.org/

Or, for total peace of mind, sell it without the hard drive.

Remember to wipe the disk first, no matter how you delete and format the partition.

As jaytkay and dpworkin said, use a program designed to purge your data even from people trying with software. Programs like that overwrite the data thoroughly with garbage.

Use dban as @jaytkay suggested.