Are there any AVAST users out there that can give me advice please?

I discovered from out of nowhere this morning that my spyware doctor had discovered backdoor.irc.flood on my computer. I cleaned it off and decided to use the Avast anti virus which i have as a backup. The Avast found no infections but it did give me a list of 11 folders that it was unable to scan. 8 of these were labeled yahoo anti spyware quarantine. I do not have yahoo anti spyware on my computer and should i ignore these unscanable folders,delete them, or what . I am fairly ignorant as to the workings of Avast