If you cannot use the Internet or download any required programs
to the infected machine, try downloading them from another computer (family member, friend, library, etc) with an Internet connection. Save to a flash (usb, pen, thumb, jump) drive or CD, transfer to the infected machine, then install and run the program(s). If you cannot copy files to your usb drive, make sure it is not "Write Protected
If you get an alert that Rkill is infected or not valid, ignore it
. The alert is just a fake warning given by the rogue software which tries to terminate programs that try to remove it. If you see such a warning, leave the warning on the screen and then run Rkill again. By not closing the warning, this sometimes allows you to bypass the malware's attempt to protect itself so that Rkill can perform its routine.
Also see Troubleshooting Malwarebytes' Anti-Malware