It's quite pre-Windows 7 this DLL, and it probably needs to be RegSvr32'd from an elevated command-prompt, or with UAC turned off (but that requires a reboot if it's currently on).
It's not an OS-used DLL, so it won't need to be done while (re)starting. It might help if AV is turned off during the RegSvr32 action, but usually that's not required.
Worst case it's missing some required file(s).
It's actually a fail in the installer, that should take care of things like that, but if if the installer is really old it couldn't know, ofcourse.