I was searching around for as much info on this nasty as I could, and everything I’ve found on it says it can’t infect windows vista operating system. I remebered seeing an old post on here so I looked it up.
Can you say what is the infected file name, where was it found (C:\windows\system32\infected-file-name.xxx)?
What avast! version and virus database are you using? (see About dialog of avast!)