The Erase free space function does exactly this, by writing files with random names and content to the drive until it is full, then deleting those files and overwriting the unused entries in the file table. Note however that Windows may retain copies of deleted files, in whole or in part, in, for example the page file and shadow copies retained within Restore Points; neither of these are marked as free space, so they might need to be dealt with separately.
Thanks. The references on how to do this in the documentation are vague, and in at least one case, overlooked. This needs a little work. But I finally figured it out.
New problem. I'm getting error messages like this in the task log file:
Friday, October 15, 2010 3:32:50 PM Error D:\WINDOWS\system32\Macromed\Flash\FlashUtil10b.exe did not have its cluster tips erased because you do not have the required permissions to erase the file cluster tips.
How do I give permission to erase the cluster tips?
I am not responsible for the Eraser manual, but I did write a piece in the FAQ (link below) on Getting to know Eraser 6. There are instructions there both for erasing the free space on a drive from the context menu and for creating a task in the Schedule. If there is any way in which you think these instructions can be made clearer, please let me know; I am always willing to update the post as necessary.
In Vista and Windows 7, there is a whole range of files (tens of thousands of them) that are heavily protected by the OS, and to which users (even running as administrator) will never have any form of write access. These files simply cannot have their cluster tips erased. With an OS that is installed to a new or clean hard drive, that will typically not be a major problem, as most of these files are written to the drive on first install, and their cluster tips will not contain private data (or any real data at all), though obviously this becomes less true as the OS is progressively updated and files are replaced.
So your 'error' message is not really an error at all. I am encouraging Joel to downgrade or remove error messages relating to issues that are built into the OS; he has already done this to some extent in the Eraser 6.1 development builds, and there is a Trac ticket to reduce (or even eliminate) the log entries related to system protected files.
Incidentally, I believe that, for the great majority of users, cluster tips represent much less of a security/privacy issue than, for example, application logs, shadow copies and the page file. You need means other than Eraser to deal with all of these. Computer security is not a one stop shop.
Re: Vague or inexplicit...lol
Here's some feedback on the manual from a new user's point of view.
In searching for the instructions for erasure targets, page 6 says: "There are currently four kinds of erasure targets:", but only three are listed. A reference to a 4th method, erasing unused disk space, is omitted. However the discussion and illustration in the above paragraph shows "unused disk space" as one selection on the Select Data to Erase menu.
Just a little confusing on first reading.
And I have resolved my other issues by re-reading the manual several times.