I want to completely reset my computer, and I would like to write a program that will write all zero's to my hard drives so that I can be sure they are completely reset. I know a fair amount of c++ and I have visual c++ 6.0, so I know I have the tools to do it I just dont know how. I think I need to use pointers. Any help would be helpful

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What good is it if you've got everything but the one thing that you really need?
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Athlon 1.2ghz
384mb sdram
Asus A7V133 Motherboard
GeForce2mx
Soundblaster Live 5.1
DVD-Rom 16x
Two 40 gig 7200rpm HD's
Win2k Pro