I ran into this issue, too. Alexey Ivanov's response didn't quite help me,
but it did, however, inspire me to investigate
As usual, error messages were only half-useful. In my case, the DLL wasn't missing--the installer didn't have permissions to access the folder. I didn't try running the installer as an administrator--this didn't make sense to me considering I was already using an admin account and would have expected UAC to handle privileges elevation. Anyway, like many things in Windows, this whole thing is a bit of a mystery to me.
Nevertheless, after going to