cannot reset home page on windows xp explorer v 6.0.2900

have inadvertently loaded a stupid thing on the pc – http://www.tattoodle.com/?tid={67DB4145-A120-486a-B84F-D48E384EC749}&v=12 and now my reset of home page is greyed out and inaccessible. Home page is now set to this silly site.

can someone please assist??

thank you