Hello. Dell Precision M6600 C and D ram slots do not work. An Intel Core i7-2620M processor is included,Intel QM67 Cougar Point chipset. At the bottom of the machine in slots A and B there is 2x4gb ddr3 pc3l 12800s 1600mhz ram. This goes perfectly with the notebook. However, if I add an extra 2x4gb ddr3 pc3l 12800s 1600mhz module to the C and D ram slots under the keyboard, the machine will no longer run. The fan spins up and has a dark screen. After that, I took the two rams out of slots A and B, only stayed under the keyboard and didn’t start anyway. Can somebody help me? Thanks