Honestly at this point, you can try to replace the file from another PC, or you could just run a repair install, I suggest the repair install, update any service packs, drivers, and then you should be back into your OS, data intact. There are step-by-step instructions here.
This could have been caused by a virus infection. Make sure you have a good and up to date antivirus.
If the repair doesn’t help, you might need to format the disk, and re-install the OS.
Normally, dll errors of any computer units are associated with Operating System errors. These particular errors are the corrupted system files of the Operating System. Remember that Operating System files are the most important files needed to run the OS properly. You may have to re-install your Operating System.