You can do a low level format (programs available from disk manufacturer), and then use an OS that does not pointlessly write files to any old space on the drive, such as for example Mandrake Linux, which also can be used to thrash a file (deleting it from the hard drive), although how effective it is I do not know.
To a certain extent you are a victim of yourself, you are using M$ Windows. When there is, likely as not, no need to.
