Hey, 2/3 years ago exactly (I think 3, but whatever) I purchased a pre-built PC. Some things I've had to replace, such as the PSU and the memory sticks, so the current setup is: AMD Phenom X4 955 (3.2GHz, never overclocked) ASUS M4A87TD/USB3 mobo 4GB Kingston 1600MHz RAM (1x4G, tried another one of these and neither consistently POST) OCZ OCZ-ZS550W-UK 550W AMD/ATI HD5770 (1GB) Western Digital Hard Drive In November, my Kingston 1333MHz RAM broke, like the 2x2gb sticks I originally got with the build, and so I've been using a friend's memory (which IS on the QVL). My sister bought me my current ram, a 1600MHz Kingston one (the "Kit of X" ones of these are on QVL). On the 27th, just two days later, I started experiencing problems. At first, freezes without BSOD. The most I managed to get out of it since is seven hours, during which I just left it on the desktop with nothing running. Lately, the BSODs of the friend's ram-era are back again, latest being: IRQL_NOT_LESS_OR_EQUAL MEMORY_MANAGEMENT (0x1A) This is extremely annoying, as it is hindering my ability to finish college work. So far I've tried: Testing friend's RAM and my RAM solo Testing friend's RAM and my RAM together Testing friend's RAM in all four slots Testing my RAM in all four slots Checked all connectors are in properly Underclocking the RAM to 1333MHz (if for some reason my CPU doesn't get on with it) Restoring default BIOS settings. Since the first 2x2GB sticks, the CPU has been replaced (replacing the old 400W one with the 550W OCZ one at current). At current, I get a blinking red light (the MemOK! one) with no beeps from the motherboard. I don't imagine the PSU has conked out so quickly, nor do I believe the RAM could have - Is it a case of my MOBO giving up the ghost? Thank you.