radeon hd 4870 or the motherboard

[no__name]

My pc spec is
Processor: intel core 2 quad Q8400 @ 2.66 ghz
ram : 4 gb
system : 64 bit windows 7
gpu : xfx radeon hd 4870
psu : thermaltake tr2 rx-450 watt
my problem recently started with gpu or at least thats what i believe... while doing almost anything, after some time (no specific time limit)
the gpu fan suddenly revs up making huge noise and the PC shuts down... gaming and watching HD movies seems to speed up the time of shutting down... usually while attempting to restart if the fan keeps up revving i get no display but my windows does load as i hear the welcome music.... bt if the fan makes low revoltion and low noise i get to see the display.... sometimes the pc shuts down when booting up the windows...
i tried using CCC at 100% fan speed to cool the gpu but it shows the temp doesnt go below 50C... at 60% fan speed the temp is 52-53C........ under load the temp shows about 65-70 C....... i cleaned the fan and gave it a compressed air blow and applied thermal paste 3-4 moths ago... well while playing ME 3 few days ago i saw some blue artifacts on the screen but havent seen them ever since...
im using the motherboard display now.... now for some days while running on my motherboard display driver a message pops up ""your display driver stopped working and has recovered" then it takes a restart showing a "crash memory dump" blue screen... although it happens once in every 3-4 days... im wondering is this a gpu problem or a motherboard one??
plz help......

[Tyree]

Your PSU could be the problem or lending to the problem.
It is poor quality and underpowered.
You need to be at 650W minimum with a good quality PSU for the 4870.
SeaSonic-XFX-Corsair (not the CX-GS-M Series) are top quality.

[no__name]

but ive been running under that psu for 1.5 years now.......

[Tyree]

Consider yourself more than fortunate.
All PSU's degrade over time and the low quality units do so at a faster rate.
Power Supply Information and Selection

[no__name]

i tried with a corsair 650 watt PSU ........ did not work........ still the same problem.....

[Tyree]

It's very possible the low quality underpowered PSU has damaged the GPU. Can you try a different GPU in your PC or try your GPU in another PC?

[Rich-M]

This probably is not the answer but have you tried going to mfgr site and updating the video card driver? If not do so though as Tyree states the psu is most likely contributing to this anyway.

[Tyree]

It would do no harm to try Rich-M's suggestion.