The Pentium 4 M and the Celeron M based off the Pentium 4 M do not have built in wifi in the processor. I own 3 laptops 2 P4 -M and a Celeron 4 M all use MINIPCI wifi which is a separate card put plugs into mini pci slot on the mother board. Centrino is not a processor either like some like to be but a intel standard intel states what type of processor and what mother board chipset and what mini pci wifi card the laptop maker must have in the laptop to get the Centrino Sticker. But the P4/Celeron - M processors do use less power than the typical P4/Celeron4 processor . Mini PCI cards are a some what new format that been out for a couple of years. Mainly used for new wifi cards. Which allows power to be turned on and off to the wifi card by the press of a button. On my HP i even have a light for it when it on or off my dell does not have a light but there is a on/off button for the mini pci wifi card. But on the issue of the Battery Life I get 3 hours of life with this new HP laptop but that is with Sierra Wireless Aircard 750 which is battery killer. * aircards are for data transfer from you celluar provider. But with out the aircard and just 802.11B/G I get 4 to 4 /12 hours.