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FILE WIPING/ ERASING SENTITIVE DATA FROM YOUR HARD DRIVE (source1)(source2)

What is file wiping/ why not just delete?
How many times do I overwrite?
Warnings
What is wiping free space?
Before you start free space wipe
Wiping all data on a drive
Which file wiping program to use?

What is file wiping and: Why not just delete?

There's a crucial difference between deleting a file and wiping it. A deletion leaves a file's entire contents
on your disk, until the space it occupied happens to be overwritten by a subsequent file. In the mean time, the
data can be recovered with forensic techniques. A proper wipe overwrites that space immediately so the file's contents
can't be recovered.
Here you can download a free program that will show you the files you thought you deleted from your system.

How many times do I overwrite?

For casual snoopers, 1 overwrite may be sufficient. For withstanding Police forensic aervices; 3 times
should be the minimum. Those who are likely to come into conflict with their government, should overwrite at
least 6 times.
Then again, to secure file wipe for military or government purposes it is recommended that the data is overwritten a
minimum of 35 times.
If you're truly paranoia or if you're in a situation in which you cannot afford to leave any traces at all, buy
a second hard drive and copy all files from the first drive to the second before you wipe the entire first drive
(here you can read how it's done)

Warnings:

-Never ever "save" an edited plaintext file; use "save as" instead. All versions will then remain available for deletion.
-Use a recent version of a file wiping program, especially when you're using WINDOWS NT, XP or 2000 (read more).
-Don't use the PGP file wipe option. In most cases it doesn't work the way it should (read more)

What is wiping free space?

A free space wipe comes in when you previously deleted files from your drive the insecure way. The wiping
of unused disk space means that all space available on your drive will be overwritten so that data previously
saved on it cannot be restored. (No, this doesn't affect your installed software)

Cluster tips?/ Before you start free space wipe:

When a file is loaded in memory, its cluster tip area cannot be overwritten and you will receive an error
because of this. To reduce the amount of locked files into a minimum, you should close as many applications
as possible before wiping unused disk space.
A free space wipe will: First wipe free cluster tips, then overwrite the free space, third overwrite the free
space on the MFT (for Windows NT or 2000) and finally the names of all previously deleted/wiped files will be
overwritten.

Wiping all data on a drive (Or: before you're gonna throw your computer away):

-To completely overwrite all data on a drive, it may be required to install the drive on another system because
the operating system files cannot be accessed while it is running.
(If you don't have access to another system, you need to use a file wiper that can be used from a bootable
floppy disk. E.g.: PC Inspector e-maxx (download)
-First delete all files, then overwrite the unused disk space (It is only overwritten 1x by default, so you might
want to change this.)
-Use the standart format to clear possible data remaining on the file system table.
-Yes, (only for you paranoias) now it's time to physically destroy the disk platters.

Which file wiping program to use?

ERASER (free download). Source code is released.
Gives you all the options for a PERFECT FILE WIPE AND FREE SPACE WIPE.