Yes you can you use all of them before login, but windows is already booted. The computer has to have an operating system to boot to, what James is and mikesmith are talking about is scanning before windows "Starts" not before it boots. The fact is the screenshot from the OP shows a variant of "Antivirus 2009, Antivirus360, and so on) There all derived from virtumonde which as I stated above infects several files that windows "Protects" becuase they are running. The reason why most people will tell you to boot in safe mode is in hopes that the virus itself will not be running and therefore not protected so that your chances of removal will be greater. This particular virus infects files that windows protects so the only to remove the virus is pull the hard drive and scan it from another computer or format and re-install windows, or use linux and you wont have this issue at all!