scott wrote:
>> 1. Delete all the files. (E.g., delete C:\*.*)
> 
> I wonder if you actually asked many non-geeks, what they would say if 
> you asked them how they would go about erasing all their data from their 
> computer?  I guess if you try to select-all and delete the contents of 
> drive C from within windows it's going to get stuck at some point.

If you just want to delete "your" files, you can certainly do this. If 
you want to delete the OS, you'll definitely have to do it while running 
under something else. (Obviously.) I have an external USB enclosure for 
this exact purpose. It's shiny. The company paid for it. :-D

>> Option #2 destroys some of the filesystem metadata, but AFAIK the 
>> blocks holding file data will still be intact.
> 
> Oh, I thought that "format" really went over every byte of the partition 
> and wrote to it?  IIRC there is a "quick format" option, which I assumed 
> just did the headers and stuff to make it look like it was formatted.

Formatting a drive with ext2 just rewrites the inode tables. (Or... 
something like that.) Doesn't touch most of the disk surface, and 
typically takes about 20 seconds for a large partition.

A "normal" format with FAT or NTFS seems to touch more of the disk 
surface, but I'm not 100% sure whether it rewrites every single block, 
or just the first block in each cluster. The "quick format" option just 
rewrites the file allocation table, AFAIK. (That's why it takes seconds.)

>> I am unsure as to whether #4 and #5 are different in any way. Both 
>> seem to take the same amount of time...
> 
> I think that writing zeros to the disk would make it easier to recover 
> the data, but that's just a guess.

Writing random data is theoretically best. But in either case, once data 
has been overwritten, the drive electronics can't read it back. You're 
into microscope territory. The question is whether a low-level format 
actually overwrites everything or not.

> Just chuck it on a hot fire.  Saw it in half first if you want things to 
> go quicker.

Have you ever *tried* to make a hot fire?

It's way harder than it sounds...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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