[the strange girl]

Hi every body ..I have a virus in my pc ,,[[or this what i think ]] coz when i started my pc

[[ windows xp]]the starting home page looked strange ;and it has a worning and [[sarsoor ]]walking and a big words saying [[SPYWARE WORNING]]so i started my Norton Antivirus and it found nothing and i make disc cleanup and defragment to my pc and again i started my norton antyvirus and find nothing ,.
I want to ask u :how can i know that there is really a virus in my pc ?and how can I know that a Cracker entered my pc [[with Patch ]or other things ?mmmm
note 1: My connection is not Dial up ; it s Cable [broadband connection] and the number of SENT is sometimes bigger than the number of Received??is it normal??mmmm
note 2 :if u want me to write this in Arabic ;so it is easier to u ;just tell me

thanks