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.
I've a dell laptop with me which came Windows 7 Home Basic preinstalled.I have Windows 7 Home Premium DVD with me.
My questions is that can I install Windows 7 Home Premium version on my Laptop considering the fact that Home Basic Version is currently installed?
I'm a bit leery about the installation because following message is printed over it:
"Windows OPERATING SYSTEM
ALREADY INSTALLED ON YOUR COMPUTER
Windows 7 Home Premium 64 bit
The software is already installed on your computer.Use this DVD only to reinstall the operating system on a Dell PC."
Those who don't want to contribute,better stay away from my thread especially Jimmy and R Proffit who are the so called moderators.