can delete the virus

Dear Support..

I am using Window xp and earlier “Windows has detected spyware infection and after installing microsoft anti-spyware the problem was cleared but there still one virus called Backdoor.Fivsec in my computer.

I ran Norton anti virus and update it many times but still this virus keep prompting. How can i delete this virus?

and whenever i start up the windows there a message kernels64.exe is misssing. Where i can get that file?

Plz advice

Thanks
Ken