BRL
In short, yes. When the fault first occurred all my drivers were up-to-date and since then I have completely wiped the HDD, minimised the hardware and completely reloaded Windows etc.
I've had another close down after the first post, with the error code:
BCCode : 1000008e BCP1 : C0000005 BCP2 : E16FB7FB BCP3 : BA98E91C
BCP4 : 00000000 OSVer : 5_1_2600 SP : 0_0 Product : 256_1
I think the problem may actually lie with the processor (AMP XP2000+) which might be overheating, as it's been running at about 63 degrees celsius. I have just given the heatsink, fan and processor a thorough clean and then reinstalled it with a fresh layer of conductive paste.
We'll see whether this makes a difference!