You should perhaps ask this in the Dell forum. However generally a Laptop CPU isn't upgradable.
hi,
i have a dell xps m1730 which i am extremely happy with and have saved up for over many months. i unfortunately am not that well off and had t get a T7500 (Intel Core Duo 2.2 Ghz)however i have now got enough money to upgrade as i have been offered a new T9500 (Intel Core Duo 2.60GHz,6MB L2 Cache,800MHz) for

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