It looks like "Eraser 5.8" is the best option out there for erasing files and it's free:
http://www.heidi.ie/eraser/features.php
It's not needed for most things but for pr0n, personal info, etc., right clicking and selecting "erase" instead of delete", a shell extension, isn't that hard and the files are gone for good.
It can also create a nuke disk to erase an old hard drive.
From the app's help file:
Eraser is an advanced security tool, which allows you to completely remove sensitive data from your hard disk by overwriting it several times with carefully selected patterns.
You can drag and drop files and folders to the on-demand eraser, use the convenient Explorer shell extension or use the integrated scheduler to program overwriting of unused disk space or, for example, browser cache files to happen regularly, at night, during your lunch break, at weekends or whenever you like.
The patterns used for overwriting are based on Peter Gutmann's paper "Secure Deletion of Data from Magnetic and Solid-State Memory" and they are selected to effectively remove the magnetic remnants from the hard disk making it impossible to recover the data.
Other methods include the one defined in the National Industrial Security Program Operating Manual of the US Department of Defense and overwriting with pseudorandom data.
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Most people have some data that they would rather not share with others - passwords, personal information, classified documents from work, financial records, self-written poems, the list can be continued forever. (Editor's Note: Pr0n!) Perhaps you have saved some of this information on your computer where it is conveniently at your reach, but when the time comes to remove the data from your hard disk, things get a bit more complicated and maintaining your privacy is not as simple as it may have seemed at first.
Normal file deletion is insecure
Your first thought may be that when you delete a file, the data is gone. Not quite, when you delete a file, the operating system does not really remove the file from the disk; it only removes the reference of the file from the file system table. The file remains on the disk as long as another file is created over it, and even after that, it might be possible to recover data by studying the magnetic fields on the disk platter surface. Before the file is overwritten, anyone can easily retrieve it with a disk maintenance or an undelete utility.
For example, imagine that you have been surfing on the web for a while and afterwards wish to clear any traces revealing what sites you visited. You go to your browser’s preferences and select to clear the cache and the history file, the information is now gone you think to yourself - well think again. The browser cache files can easily be restored with an undelete utility and your privacy is once again compromised.
To be sure that a file is gone, its contents must be properly overwritten before deleting. As simple as it sounds, there are several problems in secure file removal, mostly caused by the construction of a hard disk and the use of data encoding. These problems have been taken into consideration when Eraser was designed and because this intuitive design you can safely and easily erase private data from your disk.
Deleted data can be easily recovered
You have most likely already insecurely deleted countless amount of files from your drive and every now and then applications create (and insecurely delete) temporary files on your drive containing some possibly sensitive data that you would rather not share with other people. This data remains on your drive until it gets overwritten and can be viewed with simple disk utility.
This is where the erasing of unused disk space comes in handy. The erasing 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. Eraser provides you a convenient way to erase the unused disk space regularly in order to remove the remains of temporary files and other sensitive information you possibly have had on your hard disk.
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Some of the most commonly overlooked security holes are discussed below.
Paging (Swap) File
The virtual memory storage of the Windows operating system is called the paging file (or the swap file). The operating system may store any information from the memory to the disk whenever it wants. This means that the paging file may contain passwords, pieces of documents and other sensitive information.
Since the operating system locks the paging file while it is running, the file cannot be accessed using standard file operations. There are applications that claim to overwrite the paging file by allocating huge amounts of memory, but this method may freeze your computer and even then the space allocated by applications cannot be accessed and not all the available space on the paging file is necessarily overwritten.
For information on how to erase the paging file, see Erasing Paging (Swap) File.
Filenames
Unless you name your files with arbitrary names, the name of a file can reveal information about the file contents. Eraser will overwrite the filename when erasing the rest of the file.
Names of the files you have previously deleted may also still be stored in the file system table; Eraser will overwrite them when you erase unused disk space.
Locked Files
An executable file cannot be accessed when it is running, the same goes for shared dynamic link libraries and all files that are opened without file sharing allowed. The cluster tip area of these files may contain sensitive data the same way as the unused area in any other file, but it cannot be overwritten because the file is locked.
To reduce the amount of these locked files into a minimum, you should close as many applications as possible before erasing the unused disk space. Closing the applications will also free memory allowing the operating system to reduce the size of the paging file making more free space available for overwriting.
The files loaded in memory by the operating system, such as the system libraries, cannot be accessed at all while the computer is running. The cluster tip area of these files may contain sensitive information, but it is not very probable because these files are locked all the time.
Bad Sectors
When an area on the disk gets damaged for some reason, the disk electronics mark this area to contain only bad sectors. These bad sectors cannot be accessed so the data still stored in them cannot be erased either. Peter Gutmann has discussed this subject further in chapter “
Further Problems with Magnetic Media“ of his paper “Secure Deletion of Data from Magnetic and Solid-State Memory“.
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You can choose from three different built-in methods, these descriptions apply to all user interfaces.
The Default Method – Gutmann
Based on Peter Gutmann’s paper “Secure Deletion of Data from Magnetic and Solid-State Memory”, this method provides the best security. Data will be written 35 times with carefully selected patterns, which makes it unrecoverable. For more thorough description, see the Advanced Topics.
This method is used as the default for overwriting files, but has been proven to be very slow when erasing unused space on a hard disk (could be several gigabytes).
A Faster Method – US DoD 5220-22.M
Two methods based on United States Department of Defense recommendation 5220-22.M from January 1995. The data will be overwritten seven times making this method significantly faster than the default, but also less secure when it comes to hardware recovery. For a more thorough description, see the Advanced Topics.
Pseudorandom Data
All passes will be random data, which is highly incompressible. Therefore, this is the only method that should be used when erasing unused space or data on a compressed drive. The number of passes is user selectable from one to 65535. For a more thorough description, see the Advanced Topics.
Being the fastest method, this one is used as default for erasing unused disk space (one pass).
Based on the descriptions above you can choose the method most suitable for your purposes. If you really do not know what you are doing, settling for the default is your best choice. You can change the used method from the Erasing Preferences window, which can be opened differently depending on the user interface. As you may notice, you can use different methods for erasing files and unused disk space. You can also define your own, custom, overwriting methods.
On-Demand and Scheduler
To change the erasing method, open the preferences window by selecting Erasing from the Edit – Preferences submenu.
Shell Extension
To change the erasing methods, open the preferences window by clicking the Options button on the confirmation dialog box.
Notice that you do not need to select the method every time, it is usually enough to set the methods once and change them only in special cases. If you want to learn more about these special cases where only specific method should be used, you should read the instructions further.
