If you just opened the rar file then you won't need to do anything but delete the file, it's only if you run the exe or if the virus somehow self executes when you open it (Highly unlikely)
its possible the virus was disguised with a .rar extension but if he clicked it and opened an archive then i doubt it
too late now, i mean they already have control of your every file now, might as well buy new pc. the rar file extension allows dirty programs to install themselves like an os on your current os and be a parasite to it basically, sucking all its code to them. no joke they are spying on you right now through your camera
Very funny, the virus was in a sandbox and never really executed.
I have windows set up so I can clearly see if it's a fake rar or not. (ex: virus.rar would be virus.rar.exe)