While I was scanning my computer, my Norton scanned a program called infostealer.snifula . Is this a virus?

Just to let you know, I have Norton Antivirus 2009 installed. After it scanned the item, it did not say it was a virus or threat. After the infostealer, it scanned other files called adware.(something) and trojan.coder and other programs dealing with threat names. Does anyone know if these are viruses in my computer? Also yesterday, my computer shut down by itself 3 times. If this is a virus, can someone also tell me how to remove them? Also I had this .txt file called "WHATSNEW". I couldn't delete it because it was used by another program. Also as I searched through my computer and used keywords like virus, trojan, adware, and spyware. The "WHATSNEW.txt" appeared in all the searches,