As Norse is pretty hard to understand for present-day Scandinavians after less than a millenium, I think the language from 1500 years before that again is hardly easy to understand, regardless of training in Norse.

Mss32.dll is not any more important than many other files that RTW depends on. It concerns the Miles Sound System Library, used in lots of applications including Winamp and RTW. It appears that some RTW versions don't come with this file, or with a wrong version.