Something really good to check it is the Trinity rescue kit. Its a iso download that is a self bootable live linux disc with a few different virus scanners the website even explains in detail how to use it.
http://trinityhome.org/Home/index.php?wpid=1&front_id=12 It will download files temporarily to the ram drive it creates for scanning. It can scan with F-prot, avg, bit defender. The best part is its a command line scanner it is a bit more difficult to work with but its faster. You can also look for a self bootable version of kaspersky and i believe there is even a bootable version of antivir.