My father in law has an old XP computer. It got virused, and running from a AV boot CD it shows volsnap.sys has a rootkit. So I need to replace this file, not just delete it (important system file). Thoughts? I am gearing towards format/reinstall, but I'm just wondering if there's anything anyone has done here. When I run AV from the OS, it doesn't show this infection. Malwarebytes, Sophos show clean.