Computer shuts off within 5-15 minutes after network cable is connected.

[Stealth3si]

Here are the computer specs of the computer in question:

Ultimate SP1 64-bit
Xion 600W PSU XON-600F14R-201
Asus M2N32-SLI Deluxe Motheroboard
nVIDIA nForce 590 SLI Chipset
BIOS Revision 1402
NVIDIA GeForce 8800 GTS 640MB
AMD Athlon 64 X2 Dual Core 6000+ 3.15 (15 x 210 FSB)
Muskin 4GB (2 x 2GB) 991587 DDR2-800 SDRAM 5-4-4-12
Koolance EXOS2 Watercooled
OS Drive: Seagate Barracuda ST3500820AS 500GB
DATA Drive: Samsung HD501LJ
NVIDIA nForce 10/100/1000 Mpbs Ethernet
Realtek RTL8187 Wireless 802.11b/g 54Mpbs USB 2.0 Network Adapter

The CAT 5 Ethernet cable network cable is attached to our main Linksys WRT320N DD-WRT router ---> Motorola SB5101U DOCSIS 2.0 Cable Modem ---> Coaxial cable from wall outlet. Another computer is also directly connected to the same router via CAT 5 Ethernet cable and two more computers are wirelessly connected to the same router and none of these three PCs are experiencing issues so this should rule out the router as the culprit.

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The issue/symptom/scenario: If I leave the computer on (even for hours) with no network cable attached to the computer, it does not turn off. But as soon as I plug in the network cable, the PC will shut itself off within 5-15min.

Based on the same scenario as described above, here are the troubleshooting attempts I made without success, except for numbers 4 and 6:

1. Switched to different network cable and router port.

2. Disabled Network Adapter connections in "Network adapter settings" for both the onboard ethernet port and wireless adapter.

3. Ran MSCONFIG.EXE and rebooted in diagnostic mode. Only basic Windows services are loaded. No startup programs are loaded.

4. Rebooted in Safe Mode with networking but could not establish any network LAN/WAN connection. Computer did not shut off!

5. Cloned entire hard disk to another hard disk and switched SATA data and power cables on the same computer.

6. Installed fresh Windows on different hard drive on the same computer. Computer did not shut off!

Out of those 6, only numbers 4 and 6 were where the computer remained on and didn't shut off at all after the network cable cable was plugged in.

Cause: What could be the problem?

Solution: How could I fix the problem without re-installing the operating system?

[johns0]

Go into control panel/system/device manager/network adapters/nforce controller and click on it and select the power management and uncheck 'allow the computer to turn off this device to save power',just guessing what the nforce ethernet is called in your system.

Do that for your wireless usb adapter as well.

[wingnut2003]

possible malware infection. based on your number 6 method of troubleshooting. sounds like the original operating system installation is infected.

[aedipuss]

re-install the nic driver? device manager - uninstall device. reboot and allow the driver to be re-installed. or download the newest from the manufacturer and install that.

[MOVIEGEEK]

Yeah sounds like malware to me, use SuperAntiSpyware and Malwarebytes to remove. Run a AV scan also(Avast, MSE, etc).

[aedipuss]

the last thing malware wants to do is shut down any computer, defeats the purpose of infecting them.

[[_chef_]]

Have you checked the mobo BIOS for some wrong settings regarding power & ethernet ports??