pc shuts down

Hello guys i have problem my pc shuts down when i'm watching video or playing game.
Everything was working flawless my pc used to be turn on for a week or more , and one day decided to clean him, i wiped dust put paste on cpu and gpu.
Then i start playing warcraft 3 and pc shut down thats when problem began, since then i run test my gpu starts to cool of when it reach 120-130c then it cools to 50-80c, i was thinking that was problem and i put my gpu in my freind pc and it worked fine.
I put new drivers , swap ram , reset bios , cpu tests all work fine no heat there , i changed power supply before few monts almost new , nothing helped.

spec

CPU Type DualCore AMD Athlon 64 X2, 2300 MHz (11.5 x 200) 4400+
Motherboard Name MSI K9N Neo v2/v3 (MS-7369) (3 PCI, 2 PCI-E x1, 1 PCI-E x16, 4 DDR2 DIMM, Audio, LAN)
Motherboard Chipset nVIDIA nForce 560, AMD Hammer
4 x Transcend 512 MB DDR2-800
Video Adapter NVIDIA GeForce 8600 GT (256 MB)
Network Adapter VIA Rhine III Fast Ethernet Adapter (one on motherboard don't work)
Power Supply 450w

What can it be did i maybe broken something when i was cleaning?
Thanks for all

 

When it's off i can see lan and keyboard are on they are geting power but i can't turn pc on until i plug out cable and plug in only then it work , i tried leaving pc on for 12+ hours it didn't shut down only when video or game is played

forgot to put this

 

What is the temperature of your CPU when running games?

 

Only game i play is warcraft 3 very low requirements i'm not sure how much but when i use system stability test it goes to 65 at cpu usage 100%, and when i watch videos its 35-40 and still i got shut down

 

I`ve had the same problem for week-PC just shuts down when i start video or game, cleaned all fans and heat sinks, applied new thermal paste, checked powe supply, nothing helps-all is running fine and cool and still shuts down. Even changed my old XP with Windows 7 and updated all drivers to the newest again(i had the newest on the XP)-problem still appears. I start having the feeling its one of the latest driver updates causing it, but dont know which one...