Why does my coumputer crash?

PoisonousSword

Honorable
May 21, 2013
2
0
10,510
4 years back when I bought my pc it was running so good but now it crashes if i push it a little hard eg:warframe at min setting windowed 1280x720.
!.5 months ago I could run warframe at max settings 1920x1200 and my frame rate went up as high as 60 now it just puts a random coloron my screen and the sound lags out and I HAVE to hard reset.I have tried on a fresh install of win 7 x64
nothing but the game (no viruses) and it still crashes.I initially thoght of my pc oveheating but when I overclocked all the fans (temp. does not reach 50c) so I ruled that out.The ram Is not a problem nor the hard drive.Later I thought it was the power supply but then I remembered it was 500w.So I have no more ideaswhat IS the problem.
My specs
AMD Phenom II X4 945
4.00 GB Dual-Channel DDR2 @ 401MHz
Gigabyte Technology Co., Ltd. M61PME-S2P (Socket M2)
NVIDIA GeForce GT 440 (runs normal screen at 1920x1200)
977GB Western Digital
Arctic A-500cx
 

PoisonousSword

Honorable
May 21, 2013
2
0
10,510


My case is open right next to me I can see every part I clean it every month and all the fans are fine.