Iain: Definitely do a memtest on your ram, BSOD in most cases is down to a stick of ram having a fault or not seated right.
I have an ASUS board in my machine and updated the bios with the utility that runs within Windows, I did have to manually grab the bios from the ASUS site and when I started the utility point towards it to update but it was easy enough to do.
Main thing with bios is making sure you get the right one, its easier to do than it used to be with the way boards are now numbered.
I was getting lockups and crashes on my machine until about 6 months ago, I had to keep opening my machine and reseating my graphics card. Turns out the graphics card was actually seated correctly and my issue was my modular power supply. I had used the additional modular leads to supply power to the VGA card, one of those leads is faulty and was causing the crashes. Disconnected them and used the leads that are wired in to the supply and haven't had an issue since.
JCD-Bionicman: Was your situation like mine? Did it only occur during video and gameplay? I don't know If I want to take the time to get inside my computer again, it was confusing enough putting it all together, ironically the power was the hardest part to figure out.
So If I do go inside my computer, what am I looking for?
Yeah, it was only happening when I was gaming, more so with the newer games that required the full use of my GTX 570.
Look on your power supply, if it is modular it will have connectors on one side of it with no wires coming from them (Unless they are being used for additional system power requirements understandably), dead easy to see if you just take the side off.
There will also be a thick cluster of wires coming out of the power supply on another side.
If your setup is like this literally just take the modular leads out and connect your VGA card to the wires that come out of the cluster instead, takes a few minutes maximum.
Another thing you may want to look at is the edge of the case, something when fitting expansion cards the fitting is slightly off. So when you put the screw in the back plate it tries to pull the card out of the slot. I GENTLY pushed the edge of the case in over a few millimeters to stop it pulling on my VGA card.