I had a similar problem and it turned out to be related to my Hosts file,
see
http://www.mvps.org/winhelp2002/hosts.htm
the section related to large Hosts files slowing the machine
"Wilton Smith" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>I have Norton installed, SpyBot, and NoAdware installed. They find nothing.
> Using dial up and Windows XP-sp1. Every time I dial up and connect to the
> internet, my CPU Usage (under CTRL Alt Del, Performance tab) shoots up to
> 100% and holds there for exactly 90 seconds. This is EVERY time I dial up
> and connect. I see no traffic going out for 90 seconds when I connect, so
> I
> don't think anything is phoning home. It only does this with each
> connection
> and it does it only once per connection.
>
> What could be causing this?
>
>