Yes, it can clean your computer. This is generally available for all major antivirus applications. Before installation, a quick scan of the computer is performed to detect and remove any possible viruses. This feature was implemented a long time ago to prevent viruses spread and corrupt the antivirus installer. If Sophos fails to remove the virus, then I recommend you check the search results below to pick something else like Kaspersky, Avast, NOD32, etc.