Unused Space Erasure After Reformat


New Member
There are a number of files on my computer which Eraser 6 will not erase due to the following error: "The file ... could not be erased because the file was either compressed, encrypted or a sparse file." After browsing a few other topics on this forum, I've realized that this problem might be more complex than I originally thought, since I'm not even sure how to tell if the files are compressed, encrypted, etc., let alone how to undo this.

Coincidentally, however, I'm about to reformat the hard drive on this very same computer, because things are really slow and it's freezing a lot. I've already backed up all the files I want to keep, and I'm about to wipe it and reinstall Windows Vista.

So here's the question: If I reformat my hard drive, so that all of the disk space (except for the space taken up by Windows itself) essentially becomes "unused" space, will erasing the unused disk space successfully get rid of these troublesome files? Or would an unused-disk-space erasure be affected by this same error (even after reformatting)?
Formatting the drive will delete all the entries in the Master File Table, including those for compressed, encrypted or a sparse files (which are, in fact, only special forms of file system object). At that point Eraser will wipe all the free space on the drive.

Eraser does not erase these special files directly, because doing so could inadvertently destroy data the user wishes to keep. Generally, this limitation is not a significant security issue. Earlier versions of Eraser 6 did sometimes wrongly recognise some files as special; this bug was, I am pretty sure, fixed in the current stable release (6.0.7).

Thanks for the quick reply, David.

So this means that reformatting will actually solve my problem? I figured it would, but I wasn't sure, since I have gotten errors when erasing unused space before. With a previous version of Eraser -- I think it was 5.87 -- it would always say something like "not all data could be erased" after trying to erase the unused space. It was a while ago, so I don't remember the specifics, but is this kind of error normal? And does it still occur in the newest version of Eraser?
mcb said:
So this means that reformatting will actually solve my problem?
When used in conjunction with Eraser, yes. What reformatting does is leave a clear path for Eraser to do its job. The more you want to leave on the drive, the harder it is for Eraser to work around that.

mcb said:
... is this kind of error normal? And does it still occur in the newest version of Eraser?
Yes and yes respectively. This is not the place to write a book on how Windows works with the file system (particularly NTFS) to put all sorts of inaccessible files on your drive, especially a system drive. There are some places Eraser (or any other program running under Windows) just can't reach. Eraser tells you about those things, but there is not a lot it or you can do about them, other than wipe the whole system (which, for most people, is not that practical a solution). Vista and Windows 7 have an even more challenging security model than Vista. The Eraser team have been working to get round the problems more elegantly than past and current versions of the program can manage, but it's a big job. For the rest of us, the program in its present form does a mostly decent job, and gives us far, far better security than if we just deleted sensitive files.