You may not *think* it is overclocked / overvolted, but unfortunately many idiot motherboard suppliers have
BIOS code that overvolts and sometimes overclocks your CPU and memory and motherboard *by default* even
when things are just set on "auto" and not on "overclock" settings. Sometimes the only truly correct way to run
at stock settings is to put some things on MANUAL control in the BIOS and hard code in the correct CPU / RAM Volts
and MHz.
Sometimes buggy old versions of a BIOS don't properly configure a CPU chip, so, again, using an updated BIOS
or manually controlled BIOS settings can help.
Try to reset the BIOS settings to factory defaults then go in and inspect the voltages and frequencies in the
PC Health / hardware monitoring sections of the BIOS to see if everything looks correct.
Other than that, I agree that you need to revisit your mounting technique for the retail Intel HS to ensure all the pins
do lock in place equally well, and ensure that the HS is installed flat / correctly with the thermal grease making good
contact.
Otherwise replace the HS with a better one. For around $36 IIRC you can get the excellent Thermalright Ultra 120 Extreme
these days which IIRC includes a Socket 775 backplate and which uses a bolt-through design (you must install it with the
motherboard outside of the case). There are some issues with its mounting mechanism being a bit loose and its heat
spreader plate being a little non-flat, but even so, if you're just trying to run at stock speeds I am confident that it
and a decent D12SL low speed 120mm fan for it would cool your CPU much better than the Intel retail cooler.
I'm sure there are many others that cool well enough and which are easier to install. Check the frostytech reviews on their
web site and look for recent dated Socket 775 cooler reviews. Go to the end of the article and look at the graphs where
they compare the noise and temperature performance of many heatsinks to the one being reviewed in the current article.
Find the top performing 20 or so, then go look up the reviews of those specific models on the same site, and look for
the "ease of installation" and installation related comments and find ones that are of high quality and which install easily.
Pick any one of those and you'll be all set.
Grab a tube of Ceramique or MX-1 or MX-1 thermal grease while you're at it if you like, though really whatever grease
comes with the new heatsink you buy should be totally adequate for running at stock speeds.
Personally I've always used (carefully!!!) a large flat-bladed screwdriver to press on the metal legs of the Intel HS
units to help bend the legs down near the motherboard while using your fingers to push the pin into the hole.
It is critical that the pins be rotated to the correct orientation BEFORE you try to insert them into the holes, and after
they click into place you do not rotate them further.
Since you only want to run at stock speed, you may also look into *undervolting* the CPU somewhat; many Q6600
CPUs can run totally stable at stock speeds with less than the default core voltages which will help your system run
cooler. I'd try values in the range of 1.15 to 1.3V up to but not exceeding whatever your default core voltage should be.