iexplore using all cpu ressource

I’m using Windows XP SP2 and since a few days when I log it’a very slow. I opened task manager and iexplore.exe is using 98% and more of the cpu.I have to do an END TASK on it. Any ideas what’s the cause? I have Xsoftspy, spyhunter, spybot, MS anti-spam, Norton Anti-virus and my firewall is active. I have also run hijackthis and registryfix… thanks for your help