Permanently delete data before deploying OS

[Quad]

Hi,

I got this problem where is have to reimage loads of used computers with a custom image of XP wich contain classified information.

The image is not the problem, i build up fully working image but i'm sure i can find some classified information on the harddisk with programs like get-data-back or speccy if i want to.

I know there are some programs for such things but i guess most run manualy.. so is there any way to make sure that the data is erased unattended before i deploy my image?

I use WDS 2008 R2 to deploy the images.

Thanks