Wiping out previous internal hdd

Hi all,

i bought a new 2tb WD sata hdd (internal). plugged it, installed it, build win 7 64bit on it and now i'm using it as my primary hard disc. I used to use my 1tb wd sata hdd, now i want to completely wipe out everything in it, so i can use it as a clean and safe storage. But apparently i cannot clean windows and program files folders from the partition which is used to be my C drive. i used to have win 7 build both on 2 partition of my old hdd, i have deleted boots of older WINs from "msconfig", and old d: drive is completely clean, i want to do the same to my old C drive.

thanks for help, in advance.

it is not possible to format the old (1tb) harddrive via windows tools?

You can use a boot disk http://www.dban.org/

Just make sure you are wiping the right disk.