CPU Over Temperture (sic) Error
This message popped up at the BIOS stage, and caused the machine to power down after a couple of minutes. When the machine was actually running, the CPU was running at 95 degrees C whereas it should've been running at a much lower temperature.
After much faffing about, it turned out that I had not properly seated the stock fan/cooler that came with the Intel Q9550 CPU. This is, in fact, much harder than it looks - whilst the cooler has four little "feet" that plug into the motherboard, this is actually very difficult to do, whilst the motherboard is in the case.
In the end, I pulled the machine apart again, and seated the CPU *and* cooler on the mobo with the board on the desk ( actually sitting on a pad of paper ). Despite this, I still found that I needed to flex the mobo somewhat, which felt a bit strange. However, everything fitted together and the machine has been running consistently, at 30-35 degrees C, since then.
The moral of the story ? Check the fitting between the cooler and CPU.
PS It's worth noting that the Intel CPU comes with some pre-applied thermal paste - I didn't need to replace this, despite having fitted/removed the cooler many times - if I'd continued to experience problems, I'd have been down the PC store to get more paste ( Shippams will NOT do ).
