You may get a bit more battery life but **BEWARE** if its a new laptop you may have great difficulty getting the correct drivers for XP. **DO NOT** reformat the hard drive until you are absolutely certain that you have all of them downloaded and burnt to CD ready to get your XP installation running smoothly. Without them you may end up with an unstable system or worse still one that won't even boot. Post make and model of laptop on forum for more advice. The other thing to be aware of is that you will probably not get any support from manufacturer or dealer if you have problems after changeing O/S.