if an image is all you want to literally duplicate the data, master boot records and all the other information there are a few tools that will duplicate the disk without any risk to the existing disk.
1. Norton Ghost - use a commercial dos based version. Version 7 springs to mind. (My Pick)
2. HDClone 3.2 - need an exact duplicate of the HDD for this one. Or at least last time i used it it wouldn't create an ISO or image, but it was free and did the job quite well.
3. Acronis True Disk Image.
I have used all three and all three have their quirks but can do the job of just duplicating the data so that someone else can have a fiddle. I used all three to image ATM Hard drives in the past quite successfully and Norton if by far my favorite.
I can probably hook you up with a Norton Ghost image, what format is the HDD 2.5, 3.5, SATA, PATA, SATA with a connector like you see on HP and some Compaq's? Need more details.
If no-one else will help you I can pop over with my ATM toolkit and laptop and give it a go. We won't frack the HDD the worst that might happen is that the drive is encrypted and you will need some more serious tools.
You got my number if you need me. I can't help yopu with the code but an image should be all too easy.