Can I install Windows XP Home SP2 to my notebook??  

I used to have a dell inspiron 640m notebook and it came with a windows xp home sp2 re-installation cd. My Dad an older Dell Dimension 3000 desktop and I've used the Inspiron installation disc time and time again to re-install windows xp on the dimension. When i used the installation disc on another pc i noticed the installation only gives 30 days until you have to call and get a new activation code. This code is diffrent from the product key you see attached to notebooks and desktops. So my question is, if i buy one of the new dell inspiron 15 notebooks, could i unistall windows vista and install windows sp using my old inspiron 640m installation disc? I was thinking that maybe it worked with dell brand computers without having to enter an activation code. Also, does the inpiron 15 come with a vista installation disc in case the xp installation isn't successful? Any help will be appreciated. Thanks:')