Hi ther.I instalt a week ago avast on my vista laptop.I ran a full scan of local drives and after 20mins of running it come up 'unable to scan'.I know that some files cannot be scanned,but in my case all of the files showed 'unable to scan'.I uninstalled and dawnloaded avast again,the same thing happend!ps.i' n a novice,so please as simple as possible,thanks!