DLL files are part of codes and information that are used by many of the programs on your machine. They are all linked to the Windows Registry and improve the speed and memory effectiveness of your computer by using an identical code to run various tasks processed by various programs at a time. The rundll error arises when a program is not able to access this particular code.
This error can arise because a DLL file has been infected by a virus or is missing on the system due to a some form of spyware. As the programs using this file will not be able to access it, there will be a rundll error to tell your system that the program cannot be loaded due to the missing code/file.
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