Ya so I OC'd my Q6600 to 3.0ghz and had the stock HSF (risky I know, but I was willing) and I had it running 24/7 for quite some time and managed to play a lot of Crysis on it while it was OC'd.
 
So here's the part where I have to be upfront.....the temps were running at 70c for the first core and the others were running their respective norms for quite some time.  However I reset my computer to give it a break and lower the frequency back to stock and that's when the trouble started.
 
First of all when I rebooted my system it shut down upon coming back up, then shut down again....and shut down once more.  I'm thinking that was my CMOS being reset to defaults cuz something went awry.  So I went into my BIOS and noticed that CPU clock frequency control had been set to disabled (Was enabled) and that it slapped things back to normal and was running @2.40ghz yadda yadda...so I check my POST and it says Q6600@2.40 (233x9) and life was good.....until I started to boot up Vista and a huge a** blue screen of death out of nowhere saying nothing but instantly flashing and resetting my rig.
 
A handful of occasions during this recent dilemma the BSOD would say Driver IRQL_NOT_LESS_OR_EQUAL.  Now i've had this problem before but the solution was to up my DDR2 voltage cuz my sticks run @ 2.1v and the boards default was 1.8v so that never happened again.  However that only popped up once, now the BSODs are quick flashes that don't say anything except a recent hardware change may have effecting things and it insta-resets my rig.  
 
What i'm trying to ask here is, did I FRY my Q6600?? cuz it was working fine at one point, the POST detects my CPU....WHAT COULD IT BE???!! sorry for the caps but this is leaving me really frustrated
 
Any help at this point would be well appreciated, even if you tell me my CPU is done that's all I need to know, I mean these Q6600s are cheap so I have no problem buying another one, I just don't want it to be a memory or board problem.

Update:
 
After letting my rig sit for a bit (couple hours) it can boot into Vista, but then just randomly BSODs with no error just saying some random crap with no specific code and reboots.
 
Everything is running @ stock at this point (except ram voltages)
 
 
Oh and one more thing, whenever I go back to try and enable CPU Host Clock Control my computer boots down and reboots itself several times only to reset it back to disabled

Probably not. Try downloading Kubuntu 7.10 and burning an ISO image on to a CD. The entire OS will run from the CD. If it runs good then it's probably Vista throwing a fit.

Edit: ISO Recorder v 2 will make burning an ISO easy.

 
 
So I just burn that to a cd/dvd and make it boot from the disc?
 
edit: Thanks for the response btw, i'm just really freaking out.

Well... Smoke~checked PSU could take all kinds of stuff with it.   But if it Posts and gets to Windows it's a reasonable to presume your CPU is still OK.
 
The IRQ error indicates a memory problem of some kind. But in this case that could be a symptom of something else.

 
 
I'm thinking maybe i've done something unforgiveable to my CPU Cache? i've heard that the IRQL error can sometimes mean that the cache is fubar.
 
And my PSU is a Rosewill 750w, maybe 2 weeks old? if that?

UPDATE:
 
I booted into Vista via safe mode and it worked (for a change) and i've been stable in it for atleast 5 minutes, however i'm getting these pop up errors saying things such as Windows Explorer has stopped working and to close the program, now correct me if i'm wrong but without Windows Explorer you can't do crap.
 
So it's something inside my OS, but what? this is insane.

OK - Rule the PSU out for now...
 
 
I tried to check your profile for system details, but you dont' have it filled out.  
 
If it's saying System Change, blah blah blah.... Let's try to rule out a corrupted file.   Pop into the Bios and set your system to boot off the optical drive.  Restart, then shut down and start again with your Vista install CD in the optical drive.   It should take a good g*ddamned long time to start, but it will check the installation and offer to repair - Tell it yes, and see.

Yes, burn it with ISO Recorder v 2. You can also get Ultimate Boot CD and use it to check your ram etc.

Hrm well safe mode disables windows explorer so I can't do anything, at this point i'm confused as to whether it's Vista itself or if it's hardware

I've never seen so many blue screens in my life, the day I go Intel/Gigabyte sh*t hits the fan.
 
Don't get me wrong I think my Q6600 @ stock ran faster than my 4800+ did anyday.
 
Now it's BSODs all over the place, can't even get into my OS just random crap.

Clear the CMOS memory take the battery out of your mobo for 5 minutes.

as a poster above said, could potentially be a memory issue.  How good is the ventilation in your case?  You could have inadvertently overheated some of your ram.  Try swapping out what you have with a module you know works, and see if that helps...

Vista doesn't BSOD without a reason and it's almost always hardware.  I'm with rayzor start pulling ram.  

Download UBCD and test RAM, CPU, and HDD

to start windows explorer, open task manager, then go to file>new task.
then type in explorer.exe

Use memtest86 to check memory without an OS:
 
http://www.memtest86.com/memtest33.zip
 
That installation works for a startup floppy or CD; pick that device to boot from in BIOS.
 
If something fails, try to rule out sticks by running one channel at a time and adjusting RAM voltage/latency/frequency.  It's possible that through overvoltage/overclocking, one or more of your RAM sticks now need slightly more voltage to remain stable.  Remember that DDR2 is 1.8V stock and not to go higher than 2.0V if you want to avoid damage.
 
I had RAM go bad on me before - very common when overclocked at high temperature - and the problem is that bad RAM eventually corrupts the OS installation.  If you find a positively faulty module (consistently errors out after a few minutes while another does not), keep in mind that you may have to reinstall Vista with the good stick.  OS corruption is hard to repair.

did you remove all other cards?
Ie, PCI?
try to boot asthte minimum
I used to get these errors when my windows XP installation got corrupted, and fuxed the videocard drivers

The easy way: restore OC options...
 
Install vista again - you'll know for sure then... The fact your PC POSTS etc says its to do with OS.... You shouldnt lose any data - follow the instructions carefully - should give an option to remove previous installation of windows....  
 
> I wouldnt want my cores (or any CPU) running at 70C for any length of time...

Thanks a lot for your advice guys, sorry I haven't replied in awhile my comp was fried as stated.
 
It turned out to be a RAM issue.
 
I currently own Mushkin Enchanced DDR2800 (2gigs) and they run at a stock voltage of 2.1v and apparently my motherboard only ran it at 1.8v which was leading to a lot of the BSOD problems.  However I upped the voltage by 3 making it 2.1v and OC'd my Q6600 to 3.0ghz and I think something went wrong between the two so I had to up the volts to +4 so technically I don't know what it's running at but it seems to be stable and i've been rockin out with no BSODs since.