Bat file shredder... help?

Im guessing thisnis the closest forum to programming, so pardon me if its in a bad zone.

Ive been toying with this idea for about, oh about 5 hours now and figured Id finally start a thread and ask your opinions about it.

Im looking to create a DOS boot disk with a batch file on it. this file will format the C:, which is easy enough but then I need it to write crap to the entire drive, format again and repeat the process X times.

this is obviously to make a batch HD shredder... that is wipe a drive so that no data is recoverable.

The problem Im experiencing is how to get the script to recognize the drive is full. Id also like to try to get the drive to fill with useless info in a better manner. I had originally set a script that saved "write.bat" <-- a program that saved write.bat to C: then called itself, thus self propegating and unfortunatly totally clogging the systems resources after the 20th or so copy because the files kept doubling and once it was trying to save a few thousand copies of the program, even though its so small the system would hang. Hey, it sounded like a good idea at the time. :D

so... thats the idea. any s***estions?