Windows XP/Internet Explorer

Hi there,
I was wondering if anyone has/had a similar problem. I’m using XP with IE 6.0 and when I go to browse certain websites, the page takes anywhere from 1-5 minutes to open. This only happens with XP, not Windows 2000. An example is UPS.comwhen I click on the ship icon. It takes forever. All my settings are set to low security and everything is enabled. Does anyone know what the problem is and how to fix it?
Thanks.