It means the DLL is in a WOW64 virtualized location (such as C:\Program Files (x86)\ instead of C:\Program Files.
Because of the way WOW64 works, when someone running a 32-bit program tries to open C:\Program Files\ they will actually be opening C:\Program Files (x86). This means that if the registry entry shows a 32-bit "autorun" entry for "C:\Program Files\path\something.exe", the system would in fact be running "C:\Program Files(x86)\path\something.exe" - but because Autoruns is running as 64-bit, when it tries to look for "C:\Program Fiels\path\something.exe", that path isn't virtualized, the exe isn't there, and so autoruns (wrongly) concludes that the path wouldn't run.
The tl;dr is this isn't a problem with Windows or a problem with the DLL. It's a bug in Autoruns.
Even though Autoruns is clever enough to look for programs and DLLs in WOW64 registry locations, it's not smart enough to look for the paths those registry entries show with WOW64 path translation enabled. Consequently autoruns ends up failing to find the program that is, in fact, there - and then wrongly colors it in leading to this whole confusion.
For reference: Never download DLLs from the Internet. DLLs are not programs, and the overwhelming majority of DLL-download sites will install adware onto your machine. DLLs with the same name can operate very differently, and it can destabilize your entire operating system if you start replacing them.
In the unlikely event that a DLL were to be corrupted (although it isn't in this case), the correct thing to do is to uninstall the program and reinstall it. The installer is responsible for making sure that the correct DLLs are put in the correct place. Don't modify them yourself.