Thanks for the advice ....
How do I check my power supply, I presume the supply in the base unit ? (I am running a two additional fan units on the base unit, plus two HD fans ... but they are fairly low wattage).
I have suspected the CPU temp, especially since ASUS boards have their own CPU temp sensors, but have switched off most off the temp related stuff in the BIOS ....
Is it standard for a CPU running hot to reboot, or will it just freeze ?
Re. Bad memory, I would have though that would just cause applications to crash rather than a re-boot ?
Keep the ideas coming !