A virus is indeed unlikely. The profiles may have been created by various services (including something like ESS), but they should not appear at the login screen. The 'hi' thing appeared because you tried to login with one of those users and practically W8 was creating the profile sub-components at that point.
You should run a repair of the OS and then after logging in with your username check out what's with the other user profiles and delete them if necessary (directly from C:\Users).