I activated Windows XP HOME Edition and this came up

what is your default browser?

the WGA is generally accomplished through windows updates, but go to internet options, from the control panel, go to the security tab, near the bottom click on the button that says reset all zones to default and try again.
go to start/ all programs/ then hit either windows updates or microsoft updates whichever is up there , this is a direct link to microsoft updates, ensure that automatic updates, background intelligence, and cryptographic services are set to start automatically, reboot and then use the windows update button to see if you can get there, this should get you in and wga can be performed through windows updates.