Hi Mom, recently bought me these 2 4GB sticks. My Dell OptiPlex 780 Dt is working very well now. I discovered this for some other people to know. You must first remove all your memory cards from your computer and then simply install the new Crucial 4GB memory cards in slots 1 and 2, leaving slots 3 and 4 empty. My computer would not boot with 2 4GB and 2 2GB on my computer. After my computer booted up and I logged onto 2 sticks of 4GB memory, I shut down my computer and installed my old 2GB memory cards in slots 3 and 4. My computer booted up and I saw a total of 12GB memory installed . I've attached a diagram of what slots my computer has. I hope this helps others if they are having trouble downloading. THANKS Crucial & Revain for this article! I am planning to buy 2 more 4GB sticks for a total of 16GB on my computer. Thank you again, sincerely, Billy.
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