Computer freezing/Static sound CPU Voltage(???)

[dostarr]

Hello, I am back with another real pain in the rear.
System specs
4gB Mushkin DDR3 1333
AMD Phenom II x3 720
XFX Radeon 4870 CrossfireX'd
m4a78t-e Asus motherboard
Power supply

Heres the issue:
Whenever I stream media or am loading a game (I think this may be high processor use....not too sure) my computer will crash and have this horrendous static repeating sound. Second issue is sometimes I will just downright freeze on boot etc no real explanation, but no static sound.

Thanks in advance, this problem is ruining my life....

 

[jsc]

What kind of PSU?