BSOD Memory Management Error - On Boot and in-game (GW2)

Hi All. As per the title, I've had several BSODs of late. I've had at least one while playing Guild Wars 2 and at least two upon boot. The last couple were cited as a 'memory management' error, which I took a mental note of. I have two sticks of 4gb DDR 3 ram which I took from an old system to use in a new build pc I made last week. I had my suspicions that a slot on the old pc motherboard...