I've got my Q6600 totally stable at 3ghz with stock volts of 1.3v. Everything else is on AUTO though, so I guess I need to find some patience... By totally stable I gave it 24 hours prime smallFFTs.
Heh . . 24 hour Small FFTs primes! That's pretty extreme!
It's pretty common knowledge that Prime Small FFTs is a very rough guide to CPU stability only, that test puts a lot of pressure on your chip and pretty much bypasses the rest of the major system components. A system that is Prime Small FFTs stable can crash n burn very quickly once you play a game or perform some NB/Mem intensive tasks!
I've recently discovered that Prime Small FFTs is actually not 100% when performing *isolated* CPU testing and can give a false thumbs up but the processor will still fail due to undervolting/overclocking. In the scenario I encountered the fix for my random rebooting was to adjust the vCore up a few micro notches.
So basically don't rely on Prime Small FFTs giving you the all clear and instead use it as a real rough guide, even though it runs for 12-24 hours your chip may still need a little extra vCore
I'm ever changing my cooling solution, and the max it got to was 40 degrees on load, so happy happy with this clock at the moment, but need more though, its like a drug.
When you say you "need more" are you talking about more MHz or more cOOling?
If it's the former then you are showing signs of overclocking addiction, if it's the latter then you are showing symptoms of an overcOOling addiction heh!
It's deffo a good standard practice to keep your hardware nice and cool but you have to watch out for cooling for coolings sake, the reason you want to cool is to allow your hardware to be overclocked and run faster and in some respects to extend its lifespan!
But is there a certain way to tell what's failing? I tried clocking this cpu higher for absoloutely ages, with no success. I could get it stable 12 hours prime95, but then as I'd start using normally for a few hours it'd BSOD
Well you know what they say,
if at first you don't succeed, try try again! . . . .also
knowledge is power . . . .and not forgetting
all good things come to those that wait! 
There is a slim chance you have a Mc pOOp CPU but mores the likely you are doing something wrong/making a basic nOObilla mistake, without knowing more about your set-up and seeing some CPU-z screenies it's hard to help further . . .
regarding the BSOD there is every chance that even though Prime Small FFTs led you to believe your processor was stable at the XYZvCore you set . . your chip in fact needs a *little* extra voltage to run fully
Real-World stable i.e not BSOD while you are inspecting some interesting pr0n!
But is there a way to know if it's one component more than the other? Say I'd be stable in prime and orthos, but a BSOD but no restart, that may indicate ram or nb right?
Yup that could be NB or RAM or some other aspect of the set-up like weak PSU, bad drivers, spilled kebab, etc etc, as mentioned above it could even be the CPU is thirsty for vCore but your not giving it because Prime Small FFTs misleads you!
I know that an undervolted cpu will always give me restart, it might bsod but restart. A ram or mobo error will bsod and no restart. Does this make sense to anyone?
It totally makes sense but there is no simple/quick answer.
The only way I can have any joy is too take things at my pace (i'm very slow but very methodical). If you read a lot of posts here you can see there are others who literally bang a system together and overclock it to the max straight away . . . ala "Straight in at 4.5GHz!"
Fair enough and they may just be naturally gifted and know a lot but most of the time you don't actually get to see any stability shots to confirm their overclock so who is too know if the system is good and robust.
Best to take things at your own pace and get to understand the patterns and symptoms of a stressed out PC.
I'm finding these two tools the most useful for my testing:
IBT (INTEL Burn Test)
Memtest86+ V2.11
rthdribl v.1.2
prime95 25.8
