Windows 8.1: High CPU usage by "System" process when idle

[Megalith]

Okay, this is driving me crazy. Whenever my PC is left idle for some time, CPU usage by "System" will ramp up. I have no idea what is causing it. I had thought that there was something in Task Scheduler that would run itself whenever my system was left alone, but there is nothing of the sort. I've also tried using Process Explorer to get a more in-depth look at what the heck "System" is, but it's as equally vague as what Task Manager is telling me.

Has anyone run into this?

 

[ButchCassidy]

Do you have this onboard NIC, Atheros AR8152/8158?

 

[Megalith]

No, I have an Intel board that uses the company's 82579V.

 

[ButchCassidy]

From some Google searches people have had success fixing this issue by updating the drivers. I would start with Intel chipsset drivers. Can you post your setup?

 

[Megalith]

Summary

Operating System
Windows 8.1 Pro 64-bit

CPU
Intel Core i7 3770K @ 3.50GHz 53 °C
Ivy Bridge 22nm Technology

RAM
16.0GB Dual-Channel DDR3 @ 1064MHz (9-11-11-31)

Motherboard
Intel Corporation DZ77RE-75K (CPU 1) 43 °C

Graphics
S27C750 (1920x1080@72Hz)
DELL U2311H (1080x1920@60Hz)
4095MB NVIDIA GeForce GTX 680 (EVGA) 42 °C

Storage
238GB SAMSUNG SSD 830 Series ATA Device (SSD) 40 °C
0B SAMSUNG HD204UI ATA Device (ATA)
0B SAMSUNG HD204UI ATA Device (ATA)
0B SAMSUNG HD204UI ATA Device (ATA)
0B SAMSUNG HD204UI ATA Device (ATA)
0B SAMSUNG HD204UI ATA Device (ATA)

Optical Drives
HL-DT-ST BD-RE BE14NU40 USB Device
ELBY CLONEDRIVE SCSI CdRom Device

Audio
CA DacMagic Plus Audio

According to the Intel Driver Update Utility, all of my drivers---aside from audio and ethernet---are up to date.

 

[JBark]

I've seen the same thing on a couple Sony laptops, 100% CPU usage after a a few minutes at idle. This helped for me (scroll down to the bottom for the proper fix):
http://superuser.com/questions/497500/disable-automatic-maintenance-in-windows-8

When I was originally searching for a fix, I also ran across mentions that certain Intel GPU drivers would cause a similar problem, but that wasn't the problem in my case.