Hi I've just bought a DDR3 4Gb ram to install on my PC. There are 4 RAM slots, alternating between blue and black. My original RAM is 2Gb. Once I plugged in my new 4Gb (single piece) onto any of the slots with or without the old RAM, the computer would give out an alarm sound when the power is turned on. What could be wrong? Defective new RAM? New RAM not compatible with my PC? As long as I can fit in the new RAM, it'a compatible right? Or should I buy 1Gb RAM for each slot? New RAM is Kingston 4Gb PC3-10600 1333Mhz Thanks!