How do I completely delete everything from my computer in one fell swoop?

[FordPrefect]

@chrisk

Depends. Hard drives have a sort of ‘memory’ that can be used to determine what was there before the sector was overwritten… with more or less success. There are cleaner programs that simply overwrite again and again and again, to the point that the data that was held there before the cleaning process was begun is almost entirely certain to be lost… one pass write a 0 in every cell, then write a 1 in every cell… maybe then alternate, and so on.

Some BIOSes have had a “Format to 1 bit” option which would forceably write each bit since even a format can leave “shadow” data. Not an issue if you are hiding files from a 15-year odl, but if you are trying to hide your clandestine activities from the NSA it might come in handy

[Duckster]

For a Windows machine, why not use Microsoft’s own tool, delpart.exe to delete the partition before using fdisk?

There’s also KillDisk.

Security is relative (pun intended).