Cygwin1.dll errors are caused by situations that lead to the deletion or corruption of the cygwin1 DLL file. In some cases, cygwin1.dll errors can indicate a registry problem, a virus or malware issue, or even a hardware failure.

Follow these steps in the order presented to try the most helpful solutions first.

Install Cygwin, the source of the cygwin1.dll file.

Recover cygwin1.dll from Recycle Bin. Besides installing Cygwin, this is the easiest solution for a "missing" cygwin1.dll file, as you may have accidentally deleted it.