Windows Server 2012 R2 Cannot register certain DLLs

I'm having an issue with a Windows Server 2012 R2 server I've inherited. It started when I was trying to figure out a problem with VSS which didn't allow it to take a backup. One of the suggestions was to un-register and re-register some DLLs; however, now I can't re-register some of them.

I get the following error messages - which are different for different DLLs.

• es.dll
• vssapi.dll

The module "xxxxx.dll" was loaded but the entry-point DllRegisterServer was not found.
Make sure that "xxxxx.dll" is a valid DLL or OCX file and then try again.

• eventcls.dll
• Vssui.dll
• swprv.dll

The module "xxxxx.dll" was loaded but the call to DllRegisterServer failed with error code 0x80070715.

This obviously stops VSS from working. When I try to do a vssadmin resize for example I get an error in the Event Viewer:

Volume Shadow Copy Service error: Unexpected error calling routine GetProviderMgmInterface. hr = 0x80042304, The volume shadow copy provider is not register in the system.

I've done quite a bit of searching but haven't found anything that I can use.

I've done chkdsk with no issues and a sfc /scannow returned that "sfc windows resource protection found corrupt files but was unable to fix some of them". I tried sfc /scannow in safe mode with the same result.

Any help would be greatly appreciated!