I have a Dell Studio laptop that got some kind of virus and will not boot up any more can I just get a new hard drive for it to make it work like to give it to my 9 year old to use for school ?
As long as you have the 7 disc and key you'll be fine.
Once you get Windows installed, you just go to http://support.dell.com, plug in your service tag, and download all the necessary drivers for the laptop.