Hi,
If you have an older laptop be careful of the recomendations from Crucial and your laptop maker because they are wrong. I have an Acer TravelMate 8200 series laptop Acer claims this laptop supports 4Gb and Crucial also said you can use this 4Gb kit to get 4Gb memory. After some research and expense I have found that machines using the Intel 945 Chipset will never give you 4Gb memory because of a limitation of the memory chipset which is 32-bit hardware. If you buy this memory for a system containing the Intel 945 Chipset you will probably get just over 3Gb of memory in reality. I ended up with 3071MB. I am not sure how this affects the dual-channel capability of the memory.