Most likely it's background or idle time tasks. Vista has a number of
maintenance type scheduled tasks. Some work from a fixed schedule
and others are triggered. Some will run when the system has been at
an idle state for a period of time.
Best to use a tool, such as SysInternals Process Explorer. It can give
you very exact information on what process(es) are running the system
resources used by them.
Download and tool description here:
"GT" <GT@discussions.microsoft.com> wrote in message
> My CPU usage keep going up from 1% through 36%, 46%, 50% randomly and then
> goes back to 1% again. CPU usage keep going up and down this seem to
> when i hear my harddrive make a whistling sound. I disable my antivirus
> still does that and it also happen when computer is not being use.
> Is this CPU usage activity normal in Window Vista?