The problem with water cooling, and a mistake many inexperienced alternative cooling users make is they forget other components need cooling too. Motherboard engineers and designers engineer critical components (the chipset and voltage regulators come to mind) to be physically located in close proximity to the CPU. The reason for this is so they can take advantage of heat extracting air movement from the CPU fan. Alternative cooling users often mistakenly neglect these critical components.

So when I ask about heat, I am also concerned with heat of the chipset, the graphics card, memory, drives, etc.

I still think that drivers are the problem

And certainly it could be - but remember, you said you installed your old card and it shut down too. So that points back to something else - motherboard, RAM, PSU (new ones can be bad - ).

Perhaps someone else reading has some ideas but if me, I would remove all unnecessary hardware and attempt to set that motherboard up in a minimal configuration and see what happens - and in your case, I might even try a 3rd graphics card.

One final thought - you said you have a new case, are you 200% certain you did not install any extra case standoffs under that motherboard?

Firstly, thanks very much for letting me pick your brains, you have been really helpfull and I appreciate your time.

Your final thought is quite interesting, I decided to look at the cards in the motherboard again. One that I took for granted was the SupremeFX audio board that comes with the mobo. I noticed that it wasn't sitting straight, maybe the mobo is at an angle (different size stand-offs perhaps) so I have sat that in properly now and will let you know how it goes.

Just to make sure, this is what I am talking about when I say standoff:

The brass standoff screws into the case, the motherboard sits on top of the brass standoff, and the motherboard is secured by the screw.

It is important for all to remember that cases are designed to support 1000s of motherboards of various sizes (within standard limits). The ATX Form Factor standards only stay that if a mounting hole is used, it will be in pre-defined spots. This means there will be more motherboard mounting holes in the case than the motherboard supports and that is where many (including experienced) builders mess up - they install standoffs where the motherboard has no corresponding mounting hole. This often results in critical circuits running on the underside of the motherboard being shorted out - and permanent damage to the motherboard, and in extreme cases, anything plugged into the motherboard, may be destroyed. Fortunately, permanent damage does not happen every time, and removing the standoff removes the short. Nevertheless, to check properly, you must remove the motherboard.

I noticed that it wasn't sitting straight, maybe the mobo is at an angle (different size stand-offs perhaps)

The motherboard should not be at an angle. Did you use standoffs from two different sources? If you suspect there is even a slight chance the standoffs are not the same size, or properly installed, you need to pull the board. If the motherboard is not sitting perfectly flat on top of all the standoffs, then it will be flexed when the mounting screws are secured and that is bad. Over time and several heat/cool cycles, microfractures can occur in those areas under stress. Microfractures in microcircuits may as well be gaps across the Grand Canyon.

If this PC came across my bench, I would pull the board and make sure the standoffs match 1 for 1 with mounting holes in the case. Then, as mentioned above, I might consider assembling the PC out of the case on a hard, flat, non-conductive surface - wood cutting boards work great - with only one stick of RAM, one HD, and the most simple graphics solution I could find in my spare parts bin. Disconnect all other devices, cards, modules, etc. and see if I could get it to boot. I would also make sure my motherboard speaker was enabled and would listen for beeps.

Firstly, thanks very much for all your input and time on this!

I have pulled everything to bits and re-built paying attention to every detail. The height anomally of the SupremeFX audio card I can only assume is a small discrepancy not apparent on any of my other cards. the rear-most standoffs (the ones closest to the rear panel) are actually built into the case and are not removable so therefore the height of the motherboard is predefined by Thermaltake.

I found some old (slow) RAM and tried that in-place of my Corsair Dominator RAM, still no success. Then I decided to investigate the only remaining factor, the removal of the air cooling fan in favour of a water-cooled block. Since the NB and many other chips on the motherboard are connected via cooling pipes and heatsinks which all gather round where the processor fan would be, I placed a temp probe as close to the NB chip as possible and recorded a temp of 70 degrees celcius and slowly climbing!

Needless to say I switched off the computer, cobbled together some extra fans and zip-tied them to the heatsink fins around the processor and brought this temp down to about 45 degrees.

I have been using PC Probe to monitor voltages and temps, and from time to time I get a warning about a low 1.2VHT, CPU VTT or SB core (sometimes dipping momentarily to 0V!!!). The voltages at this moment are as follows:-

DDR2 TERM - 1.01V
CPU VTT - 1.26V
SB CORE - 1.52V
1.2VHT - 1.25V
+12.0 - 11.65V
MEMORY - 2.03V
NB CORE - 1.25V
+5.0 - 5.00V
+3.3 - 3.22V
VCORE - 1.31V

No blue screen so far (but when it has been a couple of days rather than a couple of hours I will be happy)

Bah...another blue screen

I think, tomorrow i will pull the mobo again, remove the water cooled block and re-fit the old stock air cooler. If that doesn't work I may have to come to the realisation that I have cooked my mobo and go for a new one

One thing I can also try;

I have a brand new, boxed Corsair 550W power supply with a dedicated 12V rail rated at 41A. Once this has been changed that will only leave the motherboard and processor that haven't been swapped.

Reading through ASUS forums, I saw a post about PC Probe reporting intermittent 0V power readings and someone replied saying it was either a faulty motherboard or power supply. I was getting a voltage alarm from PC Probe every 2 to 3 minutes, so I changed the power supply. So far I have been on for about 30 minutes without any alarms so I am almost convinced that I was supplied a faulty power supply. I say "almost", it's only been 30 minutes and this problem has vexed me for nearly 3 weeks lol

Another shut down

The voltages are all stable now, so I think I should send the Thermaltake power supply back.

I will replace the CPU fan tomorrow, if that doesnt work I will change back to XP and see if my system stabilizes (if it does stabilize with XP, then surely it is drivers?)

Well, this is interesting :-

I didn't bother to reinstall the air cooled cpu fan, formatted the HDD then installed Windows XP Service pack 2 (upgrading to Service Pack 3 as soon as I was online).

No blue screen or unexpected shutdowns in the 2 hours it took me to format the drive and install XP.

A further 3 hours of usage including some graphics intensive gameplay and no blue screen.

I then formatted HDD again during a clean Vista Ultimate 32-bit installation; as soon as the installation was finished, I entered desktop and had a blue screen. This was even worse, everytime I restarted and went to desktop I got a blue screen.

I then formatted HDD again and installed Vista Home Premium 64-bit and this has no problems.

Now my problem, I have gone to great expense to get Vista 32 (most games only work with 32-bit platforms) for DX10 etc. I can go back to XP, but after spending money on Vista why should I?

Has anyone else had this problem, could it be that Vista is installing the wrong drivers somehow? And if so, why doesnt Vista 64 do it?

OK, It's been 3 weeks now, I thought I would provide an update.

After my last post I found that all wasn't quite right still and I started to get blue screens again. So, I decided to look again at drivers since I had exhausted my hardware ideas.

I found this site for anyone with nForce motherboards and tried their driver packages:-

nForce Drivers

this seems to have done the trick for XP, later today I will try the Vista drivers and see if they work.

It has been interesting following your [most excellent! ] followups - though "interesting" is probably not what you were thinking.

It did seem to be a driver issue all along - first the card, and we discussed potential motherboard problems too. I generally like to get drivers from the board makers' sites because I (can only) assume they tested those drivers on their listed boards. Whereas it is not likely the chipset makers tested on that specific model and version number ASUS motherboard, or BFG graphics card.

What I still find interesting is 64-bit seems to work but 32-bit does not - that is opposite of the norm.

How old is that Striker? Did you check for a BIOS update? (I'm too lazy this morning to go back and see if that was mentioned before - )