Does the red CPU LED stay lit when you first boot, or does it flash on and off very quickly?  Have you tried the PC out of the case?

Well Them!!!
 
PC is RUNNING more than 5 hours. Tonight I see if it's still on ^^
Stable!

VistaHead

Please post a BIOS template of the settings that you are currently using.

BIOS Version: P10
**System **
CPU Freq, MHz: (STOCK) 3000 GHZ
FSB Reference Clock, MHz: AUTO (1333)
CPU Multiplier: [9X]
PCle x16-1 & 16-2, MHz:  [AUTO]
PCle x16-3, MHz:  [AUTO]
SPPc->MCP Ref Clock, MHz:  [AUTO]
nForce SPP --> nForce MCP:   [5X]
nForce SPP c-- nForce MCP:   [5X]
**Spread Spectrum**
CPU Spread Spectrum: [Disabled]
HT Spread Spectrum: [Disabled]
PCle Spread Spectrurn(SPP): [Disabled]
PCle Spread Spectrurn(MCP): [Disabled]
SATA Spread Spectrum: [Disabled]
**FSB & Memorv Config**
FSB - Memory Clock Mode: [AUTO] 
FSB - Memory Ratio: (AUTO)
FSB (QDR), MHz: [AUTO] (1333)
Actual FSB (QDR), MHz: 1333
x MEM (DDR),  MHz: 1333 
Actual MEM (DDR), MHz: 1333
P1: auto
P2: auto
**Memory Timing Setting**
Memory Timing Setting: [expert] (manual)
tCL (CAS Latency): AUTO
tRCD: AUTO
tRP:  AUTO
tRAS: AUTO
Command Per Clock: [2T]
** Advanced Memory Settings **
tRRD: [Auto]
tRC: [Auto]
tWR: [Auto]
tWTR: [Auto]
tFAW: [Auto]
tREF: [Auto] 
tRFC: [Auto] 
**System Voltages** (manually set the System Voltages)
CPU Core: AUTO [1.18]
CPU FSB: AUTO [1.1]
Memory: AUTO[1.50v]
nForce SPP: AUTO[1.30]
nForce MCP: AUTO[1.500]
GTLVREF Lane 0: [Auto]  +00mv
GTLVREF Lane 1: [Auto] +00mv
GTLVREF Lane 2: [Auto]  +00mv
GTLVREF Lane 3: [Auto]  +00mv
**CPU Configuration**
Limit CPUlD Maxval: Disabled
Intel Speedstep: Disabled
xPPM Mode: [Native]
CPU Thermal Control: [Disabled]
C1E Enhanced Halt State: [Disabled]
Execute Disable Bit: [disabled]
Virtualization Technology: [Disabled]
CPU Core 0: [Enabled]
CPU Core 1: [Enabled]
 
I don't know what's happened because I'm not in home, but pc is shutdown 30 minutes ago, i'm informed.
If this all don't have success. I will Try off the case again to see what Happens =.

Well The problem is Still there, the PC is shutting down after 2-3hours of use and Start again after 3-5 hours the pc boot again and running fine, but stop function and begin again this cycle.
 
Can be capacitors problems?

I did this and the pc continue with the problem.
When the problem OCcurs, I try turn on the pc and  the board still with all leds on and after 2 a 4 hours the pc
Boot Up normal(like it's unfreezing to boot again). but still with this suck problem. The pc is not overheating. CPU are 37º Cores are 42/45º and MB 35º
NB 46º SB 52º.
 
I Will try when I can bring the pc to a laboratory to make tests.
 

Thanks I will continue trying I will run memtest, but I'm see in my board. One Black slot memory is moreless damaged. A pin have some problem, but it's not a problem to identify the memory in the slot.
 
I think it's one of the problems =.;

^^^Good to know.