|If you are positive that no firewall is enabled (internal Windows XP, or third party ones) than there are other posibilities:|
1. Some anti-spam and anti-spyware programs have the capability of blocking websites
2. Some websites require "Active-X" support. "Active-X" is proprietory from Microsoft, you must use Internet Explorer to view these websites.
3. If you are not already logged in as administrator (owner for XP Home) try logging in as administrator or through an account with administrator priviledges and see if that makes any difference. If this works than your problem has something to do with the settings of the "bad" profile.