High CPU usage with no programs running

[DWFreeway]

I posted this in the virus discussion too:

Alright well, let me start by saying that Ive reformatted twice, and scanned for viruses/spyware every time and I found nothing. At random times during the day, I can open up my task manager and see that my CPU usage is spiking from 50% to 70% to 100% and back again, and it is all being taken up by "System"

Eventually, the CPU usage stops and drops back down to 0%, but usually only after an hour or more. Sometimes I can reboot and it stops for a while, other times I reboot and it starts happening again. Here is the hijackthis log

Logfile of HijackThis v1.99.1
Scan saved at 2:01:39 PM, on 10/11/2006
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP2 (6.00.2900.2180)

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\system32\nvsvc32.exe
C:\Program Files\Mozilla Firefox\firefox.exe
C:\Documents and Settings\Dan\My Documents\HijackThis.exe

O2 - BHO: AcroIEHlprObj Class - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Program Files\Adobe\Acrobat 7.0\ActiveX\AcroIEHelper.dll
O4 - HKLM\..\Run: [NvCplDaemon] RUNDLL32.EXE C:\WINDOWS\system32\NvCpl.dll,NvStartup
O4 - HKLM\..\Run: [nwiz] nwiz.exe /install
O4 - HKLM\..\Run: [NvMediaCenter] RunDLL32.exe NvMCTray.dll,NvTaskbarInit
O4 - HKLM\..\Run: [KernelFaultCheck] %systemroot%\system32\dumprep 0 -k
O9 - Extra button: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Program Files\Messenger\msmsgs.exe (file missing)
O9 - Extra 'Tools' menuitem: Windows Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Program Files\Messenger\msmsgs.exe (file missing)
O16 - DPF: {6414512B-B978-451D-A0D8-FCFDF33E833C} (WUWebControl Class) - http://update.microsoft.com/windowsu...?1135016683871
O20 - Winlogon Notify: WgaLogon - C:\WINDOWS\SYSTEM32\WgaLogon.dll
O21 - SSODL: WPDShServiceObj - {AAA288BA-9A4C-45B0-95D7-94D524869DB5} - C:\WINDOWS\system32\WPDShServiceObj.dll
O23 - Service: Diskeeper - Executive Software International, Inc. - C:\Program Files\Executive Software\Diskeeper\DkService.exe
O23 - Service: InCD Helper (InCDsrv) - Nero AG - C:\Program Files\Ahead\InCD\InCDsrv.exe
O23 - Service: InCD Helper (read only) (InCDsrvR) - Nero AG - C:\Program Files\Ahead\InCD\InCDsrv.exe
O23 - Service: iPod Service - Apple Computer, Inc. - C:\Program Files\iPod\bin\iPodService.exe
O23 - Service: NVIDIA Display Driver Service (NVSvc) - NVIDIA Corporation - C:\WINDOWS\system32\nvsvc32.exe

Hope that will be helpful to anybody trying to help me... the entire list of processes I have running, having anything unnecessary closed out is this:

nvsvc32.exe
explorer.exe
5 svchost.exe processes
lsass.exe
services.exe
winlogon.exe
csrss.exe
smss.exe
alg.exe
System << eating up all the CPU usage
System Idle Process

If I missed anything to post here let me know and I will

[gerbil]

The System process is a file which stores information related to local hardware settings in the registry under HKEY_LOCAL_MACHINE.
I have no idea why yours is taking so much CPU time... but leave it be.
Btw, next time you run a HT scan [yours is clean] you could fix this one:-
O4 - HKLM\..\Run: KernelFaultCheck]%systemroot%\system32\dumprep 0 -k
- you had a crash some time ago; this is just the dump of it.
Of course, some trojans name themselves as common processes to hide in plain view.
You could try this scan- download RootKitRevealer from http://www.sysinternals.com/Utilities/RootkitRevealer.html [the link is at the bottom of their page] and place in a new folder. Read that webpage. Close all open windows, shut all applications, and then open a Windows explorer and Run RootKit Revealer from its folder...[dclick the .exe file]. Do not touch anything, even mouse, until it completes its scan.
Another free online that is excellent is Pandactivescan. Follow the leads from this webpage:-
http://www.pandasoftware.com/products/activescan?

[gerbil]

just as a test, would you disable microsoft's windows auto update via control panel for a moment to see if it has any effect? And let me know? thanks... [re-enable auto update afterwards..!]