Ya I really like XP, but I have these 4 gigs of memory that I would like to fully utilize, and I'll mainly just use my laptop for MathCad and Gaming. The MathCad is fine with XP, but I really want to try out the hybrid motherboard/graphics card to its full extent, which requires Vista 64 bit. I was also wondering if going down to home premium or business from Ultimate would increase the batter life?