A system process called "system" is killing my cpu.. located the faulty thread (acpi.sys+0x1a7c) and the faulty dll (acpi.sys). now what?

Question

a system process named acpi.sys is using up to 50% of my cpu.   The process is simply named "system" and the image name is "nt kernel & system".  i checked the properties, and the thread that is acctually slowing the cpu is named ACPI.sys+0x1a7c.  I then checked the DLL and it seems that the driver ACPI.sys is most likely the problem.. I've tried to access the file but was denied by trustedinstaller.. Ive already done a factory restore twice in the last week, with the last one having just been done, so the computer is like new and completely virus and software/malware etc free.  Ive located the source of the problem.. just need to know what to do to to fix it.  

pc:

windows 7

4gb ram

intel core i3 M 380 @2.53 GHz