We came across this problem today and thought we should post the solution in case anyone else encounters the problem.

While attempting to create an index in OSForensics the following error was encountered at the start of indexing.

Windows cannot access the specified device, path or file. You may not have the appropriate permissions to access them.
This was for the file, ZoomEngine64.exe

Then there was this following error.
Error starting indexing. Error launching indexer executable. Error code 5, Access is denied.

The problem was caused by Avast Antivirus. Avast didn't reporting any infection or malware, but it was nevertheless silently blocking executables from running and needed to be deactivated. After doing some Googling this seems to be a common problem with Avast.