Why is the System process using 40-60% of CPU power all the time?

TL;DR:

• ACPI.sys is constantly using lots of CPU power.
• Virus and malware scans all come back clean
• Drivers are up to date (GPU, Chipset, USB devices)

Possibly important info:

• This install of Win7 is on a SSD, which I had to install as a secondary boot through my primary OS (Vista). This was because my lame BIOS wouldn't let me boot from a disk or USB stick, so I need the old C:/ drive in there with Vista on it to be able to boot into Win7.
• My virtual memory is all on the SSD drive (I know this is bad for the drive but I wanted to improve performance and don't care if it dies in a few years)

My Windows 7 system is currently suffering from terrible performance issues. Looking at the processes in task manager shows that System (NT Kernel & System) process is using around 40-60% of the CPU all of the time.

A blog post I found has suggested that this is often due to a driver issue, such as a USB device or graphics driver, so I did a stackwalk using xperf (xperf -on latency -stackwalk profile) and checked the output file in Windows Performance Analyzer and it seems that ACPI.sys is causing the issue:

This is what I get when I expand the stack for ACPI.sys:

Microsoft says:

The Windows ACPI driver, Acpi.sys, is an inbox component of the Windows operating system. The responsibilities of Acpi.sys include support for power management and Plug and Play (PnP) device enumeration.

Another user fixed a similar problem by updating their BIOS, but my BIOS is Phoenix AwardBIOS and they don't provide free updates.

Should I install the BIOS/chipset drivers from my motherboard's support page?

How can I find out more about what might be causing this or possible solutions?

• HiJackThis logs?
• LatencyMon?
• sysinternals Process Explorer?

Please help, my Java benchmarks came back at 1/4 of the speed you'd expect from a slower processor!

Solution 1:

I decided to think a bit more hardware-related so opened to case to clean the processor heat sink. There was hardly any dust so that definitely wasn't the cause, but now System only uses around 1% of the CPU.

The heat sink must have not been fitted properly because all I did was remove it and put it back on and I didn't change anything else. Now my CPU graph actually goes down to ZERO when I'm not doing anything. Yay!

N.B. I'm an idiot.