No incompatibilities on adding another 4gb of kingston ram, just did that myself the moment i bought the laptop at the store itself. works fine, windows reports 8gb but says only 7.84gb is usable... usually the case with any combination of ram even if its the same ones, even on different machines. probably some memory has been allocated to the intel gpu.

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Added on September 17, 2012, 2:37 am

see if your fan does pause when the machine is idle. most laptops are suppose to, specially with ivy bridge, its a power-saving feature since the fan does take a lot of power. My samsung NP350V4X does pause its fan.

Have you monitored any of your temperatures? i used realtemp and gpu-z, playing battlefield 3 the temps highest 88-91c gpu; cpu 88c

let me know your idle temps as well, once u have rested the machine for about 30mins or more.