how can i fix my desktop?

sorry to trouble you but when my daughter logs on as a different user her desktop has turned a funny colour and keeps going dark and light. she cant get access to the net she gets the message

Forbidden
You were denied access because:
Access denied by access control list.

i checked the banned sites but nothing in there in the allowed sites www.coolsearch.com appears which i have deleted. how do i get this back to how it was. sorry to be a nusience

im on winxp pro