i just do some cleaning for my cpu..after cleaning my cpu keep auto shut down. i cant on it back..anyone can help me ?  
sometimes will off when at windows loading page..i just cant reach the welcome  page

i just clean my graphic card and fan

All you did was clean your graphics card, and case fans?  Sure you didn't kniock anything loose?

A couple of suggestions...make sure you did not knock something loose.

verify all hardware is seated good, Ram, CPU, Heat Sink, video card, power cables to all devices

make sure that all your fans are spinning

pull half of your RAM then boot up

some ideas

V/R
TakerDeep

Hi Wata, this sounds like you've may have disturbed something around the card / fan.
Check that all the dust has gone and that the cables are not snagged.
Remove that graphics card and try to start windows - it should load with default drivers - then see whether the machine will run for a period without problems. If okay, the replace your card and try again.
If the problem is still there, then check that the fan is still spinning - otherwise the CPU will overheat and lock-up.
Finally, put your card back in and test again - it could just be that the card is not properly seated.
Good luck!

thank you all for ou help. i will give it a try now

ARGH !! i have replug all the slot but still the same  

may i know is it use paintbrush to clean will have effect?

I would try blowing with an air-aerosol. If you use a paint brush, you may leave one or two brush hairs behind which could cause a short-circuit.

aww ok ty

You did not use a air compressor did you? My nephew did that a few weeks back, and did not realize that the compressor had blown minutiae amounts of water onto his circuit board, and upon plugging it in, he fried his PC. I hope this is not the case for you, as there is NO undo for it. Hate to give such a hard suggestion, but knowledge is power, that being said, I hope it is noting more then the card not being properly seated. Wish you luck my friend . . .

nope..i didnt use air compressor

Thats why I have a water filter on mine.

Check the CPU cooler, sounds like you might have bumped the cooler and if its not on right it will reboot to protect the CPU.  Does your Bios have a CPU temp area?  If so boot up to that and watch the temps.  If you have to remove the cooler make sure to clean all paste off and reapply.  Make sure all extra power adapters are plugged in, CPU power to board and your video card might require extra power.  But to me it sounds like the CPU is overheating.

If it is powering on and your are making it past the BIOS, then it definitely sounds like a Thermal safety shut down to protect the CPU!!!  If it were a loose RAM issue or other major hardware issue (mobo, chipset, cpu itself) you would get a BEEP on Post and you would not make it past the BIOS Screen and possibly not see anything at all but a black screen . I would just reset the CPU Cooling fan with fresh thermal paste and that should fix it!  As UFANS said make sure you get ALL the old paste off first before you apply the fresh paste!

GOOD LUCK!!

Captain Obvious here! Use 99% Isopropal alcohol to clean the paste off. It gets every bit of the paste and completely evaporates. I'm sure every geek on this site already knows this, but for the one guy that doesn't ...

That's a good call Sonic...I do know people that DON'T know about ISO...but it is completly safe to use.

Also dont forget about the memory suggestion as far as booting up. With my old system I had to remove two of the sticks to get it to work then but the other two back in otherwise I would get the same thing, partial boot but no windows login.