I had a call for a home machine really slow on a cable modem. Happened right out of the blue, no porn for this guy. Boot up is usual speed, apps are up to par, ISP logon fine, any web page load is slooooow. Ran everything like you have done... nothing looks amiss. [XP Home, all Windows Updates done].
Was ready to call AOL for the client and perhaps uninstall/reinstall, when LO and BEHOLD the Norton Personal Firewall was screwed up (even tho everything showed ok, ran SystemWorks etc) so shut off the firewall... it's speedy again. Redid firewall all is good.
Is your firewall ok?
Is the OS up to date w/Critical Updates?
Are you using Spybot 1.3? 1.2 is now outdated.
What happens in Safe Mode?
ZZZ.
