Well, sometimes Dell includes the XP disc and sometimes they allow you to do a factory restore which would put all the crap back on. If you have an actual Windows XP disc, then yes, you will absolutely see a performance increase with reformatting. If not, you have some other options. I'm not sure on the legality, but I believe that by owning XP you own the license to the software, meaning you can install it from another disc and be perfectly legal. If this is true ( I think it is ), you can download XP or borrow it from a friend. Look into it though, piracy is EEE-LEEEGAL.