Script to format the unused harddisk space

Hello,

I have around 200 systems with 20/40 GB hard drive, but only 8GB usable
space. This happened because our original image is just 8 GB and we keep
dumping that on all new disks too. These are also systems that automate
our assembly line and are spread world wide. So, my question is -- Is
there a way I can write a script and ask the operator to double click,
which will make the unused space usable.

Regards,
Sundar