rundll32.exe restore

I got malwares and viruses on a computer.
After some interventions, I finally deleted the malwares and the viruses BUT the rundll32.exe file was deleted by the virus too.
So the computer starts and works BUT any softwares on it don't work – when you try to run a software, you get the error message "C:\WINDOWS\system32\rundll32.exe – Application not found". Otherwise, you got a