New Help Bad

Ok, I got a ■■■■ virus that causes calculator to open when certain things are opened. It also opens command prompt and other annoying things. I scanned it norton found nothing, yet it detected it several times outside the scan. It came up with the following.
Object Name: C:\WINDOWS\system32\y91y.exe
Virus Name: Trojan.Adclicker
and it says it was found and automaticly deleated (bull). But obviously not when it came up again saying the same thing. Not to mention the side effects are still going on. I need help removing this problem so I wont have to go as far as formatting. That gets annoying. So please PLEASE somebody help. I have searched the Microsoft website for these names and got nothing. I really would be so far in debt to whoever can help clear this up.
Thanks, Rahl.