Just noticed that you're now using a different ISP than Freeserve...
You may want to check that you've got Outlook setup to use your email password when sending email - this is not enabled by default when setting up an account in Outlook.
FreeServe will let you send email without using a password to connect to their server while you are on their system (ie, using their dial-up or broadband) because they know who you are. When you are using another ISP, it won't let you "relay" email through them unless you provide your freeserve account password ... this is to stop spammers.
Simply open Outlook then goto Tools then the Accounts option from the menu.
Select the email account details you use for Freeserve, then in the Servers tab, there should be a setting under the "outgoing mail server" section called "My server requires authentication" - make sure this box is checked. You don't need to change anything under the settings button, as freeserve uses the same username/password for incoming and outgoing email.
Online guide here (substitute the Earthlink values for your freeserve ones):
http://support.earthlink.net/mu/1/ps.../5835.psc.html and here's a note about Outlook not saving passwords in XP:
http://windows-help.net/WindowsXP/troub-01.html