求救!!

求救﹕Internet Explorer Home Page被強迫改掉了.每次click open the brower, some page with the address 'about:blank' will come up, and then a pop up ads saying something like 'Your PC has been infected
with spyware. You have to click here to get fix...' It does not help if I reset the home page to a good site. Next time when I open the brower, samething happens. I am using Windows2000.

How can I fix this thing? I have Norton antivious software but no firewall.

Thanks!