The reasoning is twofold. It would appear you'd be going from a 32 bit version to a 64 bit version which would require a "from scratch" installation and that the CD you have might be for another Dell model. I can't know that for sure but, in order to upgrade, you'd need something like a Windows "anytime upgrade" version. If I was you, I'd consult Dell rather than come here if you want the best answer. With your model #, they can offer advice for their own product.

Also not advised is your warning at the end of your message. Regardless of your issues with persons here, you need to keep a cool head and not say things to stir up trouble or your post could, rightfully, be locked or deleted. Just my suggestion.