The Register: A new variant of the Popureb Trojan is proving so difficult to remove that Windows users who get infected must restore their systems to original factory condition in order to get rid of it. That means losing any installed applications and files that have not been backed up.
In a blog, a Microsoft security staffer advises, “If your system does get infected with Popureb-E Trojan, we advise you to fix the MBR [Master Boot Record] and then use a recovery CD to restore your system to a pre-infected state (as sometimes restoring a system may not restore the MBR).”