Use the Start - turn off computer - turn off instead of pushing the power button to turn off.if you do use the power button hold it in a few seconds till you hear it completely shut down.also they say turning one off with the power button can mess up the OS and stuff i haven't had that happen.
Right click "My Computer"
Go to "Hardware Device"
Click "Device Manager"
Select "Network Adapters"
Select "Marvell Yukon .....PCI-Fast Ethernet Controller--> right click ---properties--->power management-->deselect "Allow the computer to turn off this device to save power"--->Go to "Advanced" tab--->put value off for "Wake from shut down" --->value none for "Wake up capabilities"
If this doesn't work then check your BIOS
Restart ---> press F2---> go to "Main" tab --->Network boot [Disable] --- Save
I get the feeling that you just press "enter" after pressing "shut down" without checking to see what is written on the "shut down" line. Check to see that it doesn't display "restart".
It may take a moment to check what's there, but impatience can often lead to such frustrations.
The fact that the previous time you shut down it was "final" doesn't mean it will stay that way. For example, if Microsoft is set for automatic updating, it will also automatically change the "shut down" option to install new updates and could also re-start your computer on its own.
Another common cause of reboots during shutdown are minor hardware incompatibilities. Unfortunately, I can’t possibly tell you every piece of hardware out there that’s known to cause reboot problems. What I can tell you though is that peripheral devices are especially notorious for causing the problems.