Computer shutdown problem.

CoH/V keeps causing my computer to shutdown in the middle of play, basically. While running the game, my computer will simply switch off, with no warning, no error message, nothing. Has anyone else had this problem and fixed it?

-It only happens in CoH, no other program seems to do it.
-I've tried a few solutions, such as updating my drivers, turning off automatic restart to get an idea of what's wrong, turning off Ultra Mode, changing resolutions, checking for bad memory, clearing the dust out of my system... nothing has seemed to have any luck.
-It happens randomly. Sometimes I can go a few hours without a shutdown, and at least once I've had a shutdown less than a minute after coming back online.
-As I said, there's no warning, no error message, my computer simply shuts down. I thought it might be a power supply problem, except for the fact that it only happens in CoH, nothing else.

City of Heroes Helper data follows.

---System information gathered by CoH Helper version 0.2.0.2---

DxDiag gathered at June 1, 2010 17:46 (+08:00)
Operating System: Windows Vista™ Home Premium (6.0, Build 6002) Service Pack 2 (6002.vistasp2_gdr.100218-0019)
System Manufacturer: System manufacturer
System Model: P5KR
BIOS: BIOS Date: 07/31/07 16:26:24 Ver: 08.00.12
Central Processor: Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz (4 CPUs), ~2.4GHz
Memory: 2046MB
.Net Memory Report: 949MB out of 2046MB available
Page File: 3049MB (1284MB currently in use)
C Drive: (WDC WD5000AAKS-00YGA0 ATA Device) 44756MB out of 476937MB (9%) free
D Drive: (ASUS DRW-2014L1T ATA Device) zero-size drive
I Drive: (IH3032L KHC240H SCSI CdRom Device) zero-size drive
L Drive: (IH3032L KHC240H SCSI CdRom Device) zero-size drive
Windows directory location: C:\Windows
DirectX: DirectX 10
DirectX Diag version: 6.00.6001.18000 (32-bit version)

Display Notes: No problems found.
Sound Notes: No problems found.

No problems found.
Input Notes: No problems found.

Monitor: ACER P221W
Monitor's Max Resolution: (blank)
Video Device Name: NVIDIA GeForce 8600 GT
Manufacturer / Chip: NVIDIA / GeForce 8600 GT
Video Memory: 1011 MB
Driver Version: 8.17.0011.9745
Driver Date: 4/04/2010 6:55:31 AM
Driver Language: English

Sound Device Description: Speakers (High Definition Audio Device)
Driver File: HdAudio.sys
Driver Version: 6.00.6002.18005
Driver Date: 4/11/2009 12:43:02 PM

Sound Device Description: Digital Output Device (SPDIF) (High Definition Audio Device)
Driver File: HdAudio.sys
Driver Version: 6.00.6002.18005
Driver Date: 4/11/2009 12:43:02 PM


WMI Information
Motherboard Manufacturer: ASUSTeK Computer INC.
Motherboard Model: (empty)
Motherboard Product: P5KR
Motherboard Version: Rev 1.xx
BIOS Manufacturer: American Megatrends Inc.
BIOS Name: BIOS Date: 07/31/07 16:26:24 Ver: 08.00.12
BIOS Version: A_M_I_ - 7000731
BIOS Release: 20070731000000.000000+000


Registry Information for Current User
Resolution: 1600x1200
3D Resolution: 1600x1200 (Not using renderscale)
Full Screen: Yes
Maximized: No
Screen Position: 0, 0
Refresh Rate: 60Hz
Vertical Sync Enabled: Yes


Physics Quality: Medium
Maximum Particles: 50000
Max Particle Fill? 10.000
Physics Card Enabled: No


Anti-aliasing: Off
Anisotropic Filtering: 4x
Texture LOD Bias: Smooth
Water Effects: Medium quality
Bloom: 1.000 (turned on)
Depth of Field Enabled: Yes
Desaturation Effects (Sepia) Enabled: Yes
Shader Detail: Medium?


World Texture Level: Very High
Character Texture Level: Very High
World Detail Level (Vis_Scale): 1.000
Entity Detail Level: 1.000
Shadows Enabled: No
Shadow Mode: Stencil shadows
Shadow Map Shader: Unknown (0)
Environmental Reflections: Disabled
Advanced Occlusion Settings: No
Ambient Occlusion: Off
Occlusion Strength: Off
Blur: Bilateral
Ambient Resolution: Performance


Gamma Correction: 1.000
Geometry Buffers (VBOs) Enabled: Yes
Suppression of FX When Camera Close Enabled: No
Close Suppression Range: 3.000
Show Advertisements: Yes

Audio Mode: Performance
3D Audio: Yes
FX Sound Volume: 0.610
Music Sound Volume: 0.355

Show Advanced Graphics Options: No
Overall Graphics Quality: 0.500
Reverse Mouse Buttons: No
Save Login Username: Yes
Transfer Rate: 100543 bytes/second
Current Game Version: 1800.201003300904.25T5r
Installation Directory: C:\Program Files\City of Heroes

Mod files in the Data directory
No modifications found

---

As far as I know, 2 often seen problems causing this are heat or lack of power.

Initially you can check that your fans are clean, so the air flows freely. Then measuring the temperatures of your CPU and GPU might be worth doing.

Regarding power, I wouldn't expect it to be a problem with a GeForce 8600 GT, but maybe others know better.

One last thing, although I don't think it is the cause for shut downs.
You don't have much free space left on your C-drive. The recommendation is more than 10% free, so I would free up some space, and make sure your hard-disk is de-fragged.

---

Yes, check your power situation anyways and also check for heat issues. Programs like CPU-Z and GPU-Z can monitor your cpu and gpu heat levels and other relevant info that might show an issue. It's possible the stress of CoH running is the cause of your issue as it may be causing something to overheat and shut the system off. You might also consider running Furmark. It's a graphics benchmarking and stress testing program.

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