Severe Computer Malfunctioning?

[Laurence I]

that motherboard Does support that CPU(some dont) but only if
the bios is 0311 or better(please check bios version).
But it is a 125 watt cpu and you could
have chosen a 95 watt cpu. Bearing in mind its the Amps that
are of real interest, and all of those amps have to be supplied to the Mobo.

Your power supply make/model is of ultra importance..you didnt quote it.

the min req for video card is 450 watt supply. this doesnt actually tell you
the Amps the card needs, but it hasnt got as much as it could have cos
you have to give lots to the CPU.

Sapphiretech list the 6750 as max of 86watts, and it has one 75 watt pci-e connector
we cant tell how much it gets from the slot and how much from the cable.
Hopefully your supply does have a PCI-e power cable, and you are not using a molex
converter for the extra cable.

it would be nice if your ram were on the asus QVL see the link for qualified vendor list
it would be good if you werent overclocking it
it would be good if your bios were up to date in case of hard drive issues most mobos
have updates for specific hard drive models and hard drives have manufacturer firmware
updates too(have you checked?)
it would be good to check the hard drive cable/change it. make sure Snap on ones are used
as they are better quality
it would be a good idea to soak test the system, NO internet, NO AV running
maybe there is a good Asus utility to do that for you.
it would be good if the video card ONLY USED THE DRIVERS FROM THE VIDEO
CARD MAKERS SITE.
it would be good to remove any external usb devices especially keyboards/mice/printers
as they might be sucking the life out of the usb sockets. Or at least connecting LOW
performance ones, NOT flashy gizzmo ones.

TURN OFF ANY POWER SAVING FEATURES ie power scheme always ON
as a lot of software STILL doesnt support hibernation properly.

some lcd displays are Known to be poor or unreliable with respect to PnP
detection. you didnt say what monitor you were using.
======================================
my best guesses.

1 its easy to misconnect the front header connections on the mobo CHECK and CONFIRM
...all PIN connections. If the case has a preformed cable then SUSPECT IT.
...Header connections are usually Unique to mobo maker.
2 front usb cable connections, same as (1) disconnect for now
3 its always worth checking your CMOS battery, anything lower than 3.0 v suggests
...the battery is on its slippery slope. A corrupted cmos often gives vague problems
4 your power supply just may not be up to the job. Parts get extra HOT when trying like
...mad to get their Power. The harder they suck the more difficulty the supply has and the less
...likely it is to be able to supply the Amps.
5 usually when a cpu overheats everything freezes INSTANTLY. All processing, All display
...updates cease completely. This is different to a program freezing as the screen or
...cursor can be seen to do other things.
6 typically if a graphics card has issues, lines appear or squares or blocks of colour
...since you didnt mention that i doubt if its the graphics directly.

there is known malware that deliberately heats up the cpu. recently i cleaned a pc of
all facebook stuff including unloading facebook apps, and it cured it of a seemingly
overheating problem. if you are a facebook freak, then clean install the system
and never connect the internet before doing a soak test.
it should be possible in the bios to activate upper and lower temp limits for cpu operation
i suggest you check and set them, or investigate the asus utilities as im
sure they will have some for cpu temp monitoring