Everything was fine with this Optiplex 960 I bought surplused, in perfect condition. I installed Windows 7, ran updates and away we go. I hit the power button this morning and before Windows even starts, I get this error message: "MIXING ECC AND NON-ECC DIMMs IS NOT SUPPORTED BY THIS PLATFORM." System lights ONE and THREE are on, indicating a memory problem. But nothing was changed, system or memory-wise. I've never even messed with the RAM since I bought it last week. All four DIMM slots are filled, with a total of 4GB. These are Samsung 1GB sticks, all identical. I was planning on adding more RAM, anyway, but maybe I should pull all four sticks out and start with two matching pairs? What happened here? I can't even run the Dell diagnostics to test the memory - this error message halts the system. What if I pulled the CMOS battery? Would that clear this error message? Anyone? Thank you.