Steam.dll errors are caused by situations that lead to the deletion or corruption of the steam DLL file. In some cases, these errors can indicate a registry problem, a virus or malware problem, or even a hardware failure.
How to Fix Steam_api.dll is missing or not found Error || The program cannot start Error on Steam
Follow these steps in the order they are listed below to try the simpler solutions first.
Recover the file from the Recycle Bin. The simplest possible cause of a "missing" steam.dll file is that you accidentally deleted it.
If you suspect this, but you've already emptied the Recycle Bin, you may be able to recover the file with a free data recovery program. However, only do this if you're certain that you deleted it yourself and that it was working properly before you did so (i.e., it wasn't malicious or corrupt).
