I had problem with my other PC (windows xp) that ran very slow. I checked the processes running and found this wuauclt program is running. Tried to kill it but it reappear again.
I did some research on the net and found that the file is windows file for auto update and can’t be removed by kill it in the process list.
The solution is logon your PC via safe mode, find file named wuauclt.exe in c:\windows\system32. Rename it to another file name like wuaucltxxxx.exe. Then restart your PC as normal.