there was a real nasty virus going around last year
it infected every web browser and basically when u typed in a web page into the browser it would take u elsewhere such as penis enlargment [like i need it pfft], however if u googled your site and click on the organic links then it would take u there
it was very nasty to remove
to remove a virus your best off turning off system restore, delete associated reg entries in safe mode and also associated system volume folders and do a virus scan in safe mode
problem with xp is that virus are automatically chucked in system restore volumes once installed and it is a bugger to remove due to xp's resident file checker and .dll protection